Update App.php
Update App.php

Fix for #1270
Adding return to every code path
JoeBengalen/Slim,designermonkey/Slim,iinux/Slim,opengeek/Slim,AndrewCarterUK/Slim,feryardiant/slim,juliangut/Slim,dopesong/Slim,iinux/Slim,jaapverloop/Slim,mnapoli/Slim,akrabat/Slim,somjit2514/basic,samsonasik/Slim,Sam-Burns/Slim,iinux/Slim,slimphp/Slim,foxyantho/Slim,RealSelf/Slim