Don't allow creation of a new film with no name. Otherwise we try

Don't allow creation of a new film with no name.  Otherwise we try
to write metadata to the "create in folder" directory, which throws
an uncaught exception if the specified directory is unwriteable.

If we have a name then DoM tries to create the directory with that name,
which fails more elegantly and with a nicer error.

Backported-from-commit: 50aaa3789864c7330ee92e7e89ad5b6cc2155a82
Backported-from-branch: 2.15.x