Hide alerts in add form if submit was successfull

frontend/src/containers/AddForm/AddForm.tsx

@@ -63,6 +63,8 @@ const AddForm: React.FunctionComponent = (): React.ReactElement => {
             title: '',
             photo: undefined
         })
+        setTitleError(false)
+        setPhotoError(false)
         setFileName('')
     }