How to avoid SSIS FTP task from failing when there are no files to download?

I understand that you have found an answer to your question. This is for other users who might stumble upon this question. Here is one possible way of achieving this. Script Task can be used to find the list of files present in an FTP folder path for a given pattern (say *.txt). Below example shows how this can be done.

Step-by-step process:

On the SSIS package, create an FTP Connection named FTP and also create 5 variables as shown in screenshot #1. Variable RemotePath contains the FTP folder path; LocalPath contains the folder where the files will be downloaed to; FilePattern contains the file pattern to find the list of files to download from FTP server; FileName will be populated by the Foreach loop container but to avoid FTP task design time error, it can be populated with / or the DelayValidation property on the FTP Task can be set to True.
On the SSIS package, place a Script Task, Foreach Loop container and FTP Task within the Foreach Loop container as shown in screenshots #2.
Replace the Main() method within the Script Task with the code under the Script Task Code section. Script Task will populate the variable ListOfFiles with the collection of files matching a given pattern. This example will first use the pattern *.txt, which yields no results and then later the pattern *.xls that will match few files on the FTP server.
Configure the Foreach Loop container as shown in screenshots #3 and #4. This task will loop through the variable **ListOfFiles*. If there are no files, the FTP task inside the loop container will not execute. If there are files, the FTP task inside the loop container will execute for the task for the number of files found on the FTP server.
Configure the FTP Task as shown in screenshots #5 and #6.
Screenshot #7 shows sample package execution when no matching files are found for the pattern *.txt.
Screenshot #8 shows the contents of the folder C:\temp\ before execution of the package.
Screenshot #9 shows sample package execution when matching files are found for the pattern *.xls.
Screenshot #10 shows the contents of the FTP remote path /Practice/Directory_New.
Screenshot #11 shows the contents of the folder C:\temp\ after execution of the package.
Screenshot #12 shows the package failure when provided with incorrect Remote path.
Screenshot #13 shows the error message related to the package failure.

Hope that helps.

Script Task Code:

C# code that can be used in SSIS 2008 and above.

Include the using statement using System.Text.RegularExpressions;

public void Main()
{
    Variables varCollection = null;
    ConnectionManager ftpManager = null;
    FtpClientConnection ftpConnection = null;
    string[] fileNames = null;
    string[] folderNames = null;
    System.Collections.ArrayList listOfFiles = null;
    string remotePath = string.Empty;
    string filePattern = string.Empty;
    Regex regexp;
    int counter;

    Dts.VariableDispenser.LockForWrite("User::RemotePath");
    Dts.VariableDispenser.LockForWrite("User::FilePattern");
    Dts.VariableDispenser.LockForWrite("User::ListOfFiles");
    Dts.VariableDispenser.GetVariables(ref varCollection);

    try
    {
        remotePath = varCollection["User::RemotePath"].Value.ToString();
        filePattern = varCollection["User::FilePattern"].Value.ToString();

        ftpManager = Dts.Connections["FTP"];
        ftpConnection = new FtpClientConnection(ftpManager.AcquireConnection(null));
        ftpConnection.Connect();
        ftpConnection.SetWorkingDirectory(remotePath);
        ftpConnection.GetListing(out folderNames, out fileNames);
        ftpConnection.Close();

        listOfFiles = new System.Collections.ArrayList();
        if (fileNames != null)
        {
            regexp = new Regex("^" + filePattern + "$");
            for (counter = 0; counter <= fileNames.GetUpperBound(0); counter++)
            {
                if (regexp.IsMatch(fileNames[counter]))
                {
                    listOfFiles.Add(remotePath + fileNames[counter]);
                }
            }
        }

        varCollection["User::ListOfFiles"].Value = listOfFiles;
    }
    catch (Exception ex)
    {
        Dts.Events.FireError(-1, string.Empty, ex.ToString(), string.Empty, 0);
        Dts.TaskResult = (int) ScriptResults.Failure;
    }
    finally
    {
        varCollection.Unlock();
        ftpConnection = null;
        ftpManager = null;
    }

    Dts.TaskResult = (int)ScriptResults.Success;
}

VB code that can be used in SSIS 2005 and above.

Include the Imports statement Imports System.Text.RegularExpressions

Public Sub Main()
    Dim varCollection As Variables = Nothing
    Dim ftpManager As ConnectionManager = Nothing
    Dim ftpConnection As FtpClientConnection = Nothing
    Dim fileNames() As String = Nothing
    Dim folderNames() As String = Nothing
    Dim listOfFiles As Collections.ArrayList
    Dim remotePath As String = String.Empty
    Dim filePattern As String = String.Empty
    Dim regexp As Regex
    Dim counter As Integer

    Dts.VariableDispenser.LockForRead("User::RemotePath")
    Dts.VariableDispenser.LockForRead("User::FilePattern")
    Dts.VariableDispenser.LockForWrite("User::ListOfFiles")
    Dts.VariableDispenser.GetVariables(varCollection)

    Try

        remotePath = varCollection("User::RemotePath").Value.ToString()
        filePattern = varCollection("User::FilePattern").Value.ToString()

        ftpManager = Dts.Connections("FTP")
        ftpConnection = New FtpClientConnection(ftpManager.AcquireConnection(Nothing))

        ftpConnection.Connect()
        ftpConnection.SetWorkingDirectory(remotePath)
        ftpConnection.GetListing(folderNames, fileNames)
        ftpConnection.Close()

        listOfFiles = New Collections.ArrayList()
        If fileNames IsNot Nothing Then
            regexp = New Regex("^" & filePattern & "$")
            For counter = 0 To fileNames.GetUpperBound(0)
                If regexp.IsMatch(fileNames(counter)) Then
                    listOfFiles.Add(remotePath & fileNames(counter))
                End If
            Next counter
        End If

        varCollection("User::ListOfFiles").Value = listOfFiles

        Dts.TaskResult = ScriptResults.Success

    Catch ex As Exception
        Dts.Events.FireError(-1, String.Empty, ex.ToString(), String.Empty, 0)
        Dts.TaskResult = ScriptResults.Failure
    Finally
        varCollection.Unlock()
        ftpConnection = Nothing
        ftpManager = Nothing
    End Try

    Dts.TaskResult = ScriptResults.Success
End Sub

Screenshot #1: