3scale Operator crashes with "nil pointer" exception when an application CR is deleted

Issue

• When deleting an Application CR the 3scale Operator crashes with the error "msg":"Observed a panic in reconciler: runtime error: invalid memory address or nil pointer dereference","controller":"application","controllerGroup":"capabilities.3scale.net","controllerKind":"Application",..."
• The Application CR logs the following error in the status section: message: DeveloperAccount.capabilities.3scale.net "test" not found