Properly handle return code of OC_App::getAppPath
Properly handle return code of OC_App::getAppPath

* fixes #20128
* getAppPath could return false, but it was not handled everywhere

pmattern/server,xx621998xx/server,nextcloud/server,cernbox/core,whitekiba/server,Ardinis/server,pmattern/server,Ardinis/server,michaelletzgus/nextcloud-server,jbicha/server,jbicha/server,cernbox/core,sharidas/core,pixelipo/server,pollopolea/core,endsguy/server,pollopolea/core,phil-davis/core,bluelml/core,jbicha/server,nextcloud/server,andreas-p/nextcloud-server,Ardinis/server,bluelml/core,pmattern/server,sharidas/core,cernbox/core,andreas-p/nextcloud-server,xx621998xx/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,IljaN/core,pollopolea/core,jbicha/server,IljaN/core,whitekiba/server,bluelml/core,nextcloud/server,endsguy/server,cernbox/core,owncloud/core,sharidas/core,michaelletzgus/nextcloud-server,nextcloud/server,jbicha/server,owncloud/core,andreas-p/nextcloud-server,xx621998xx/server,owncloud/core,endsguy/server,IljaN/core,Ardinis/server,owncloud/core,whitekiba/server,michaelletzgus/nextcloud-server,xx621998xx/server,endsguy/server,IljaN/core,pixelipo/server,pixelipo/server,pmattern/server,Ardinis/server,pixelipo/server,whitekiba/server,whitekiba/server,pollopolea/core,xx621998xx/server,IljaN/core,pollopolea/core,sharidas/core,pixelipo/server,cernbox/core,bluelml/core,owncloud/core,sharidas/core,endsguy/server,michaelletzgus/nextcloud-server,pmattern/server,bluelml/core