Passing an empty argument to Cocoa app produces AttributeError

[mhsmith]

% briefcase run -- "" 
...
Exception ignored on calling ctypes callback function: <rubicon.objc.api.objc_method object at 0x10e2fa250>
Traceback (most recent call last):
  File "/Users/msmith/git/beeware/apps/passthrough/macOS/app/passthrough/passthrough.app/Contents/Resources/app_packages/rubicon/objc/api.py", line 333, in __call__
    result = self.py_method(py_self, *args)
  File "/Users/msmith/git/beeware/apps/passthrough/macOS/app/passthrough/passthrough.app/Contents/Resources/app_packages/toga_cocoa/app.py", line 96, in application_openFiles_
    self.impl.open_document(str(fileURL.absoluteString))
AttributeError: 'NoneType' object has no attribute 'absoluteString'

It appears to be harmless, and connected to the undocumented DocumentApp API.

[freakboy3742]

It's a bit of an edge case - in "normal operation", you wouldn't be able to start an app with an empty string as an argument. Still worth catching (and ignoring) the argument, though.

[mhsmith]

For future reference: application_openFiles_ is a method which Cocoa may call at any time, not just during app startup. This was added to allow multiple open commands to be handled by the same process, as is the standard behavior on macOS. See Podium for an example.

The GTK backend has a more generic implementation which is based only on sys.argv.