You have made some mistakes using single quotes, you have to take your variable outside the single quotes.
For this div
<div class="modalContainer" ng-style="{'background-image':'url({{selectedMeal.url}})'}">
This part is being treated as a string
'url({{selectedMeal.url}})'
Whereas you would want angular to parse this variable
{{selectedMeal.url}}
So to solve this, the correct syntax is
<div class="modalContainer"
ng-style="{'background-image': 'url(' + selectedMeal.url + ')'}">