Fix nullable and error handling in AASXFileServerAPIApiController#339

Freezor wants to merge 4 commits intoeclipse-aaspe:maineclipse-aaspe/server:mainfrom

Freezor:bugfix/fix-fileserviceserverapu-nullable-and-error-handlingFreezor/aasx-server:bugfix/fix-fileserviceserverapu-nullable-and-error-handlingCopy head branch name to clipboard