Don't abort launch on an unreadable open argument

[morozov]

On cold launch AppKit routes stray command-line arguments to application:openFile:. Before display_ui_initialised, an argument that is not a readable, identifiable file called fuse_abort(), which dereferences NULL in startup_manager_run_end because the startup manager isn't initialised yet. This declines such arguments (return NO) instead.

Repro: launch with a stray value-bearing option whose argument AppKit treats as a file to open.

open -n fusepb/build/Deployment/FuseX.app --args --gdbserver-enable --machine 48

Unpatched master crashes during launch (48 is routed to openFile:, fails to read, aborts). With the fix the app declines 48 and launches normally.

Crash signature on unpatched master:

EXC_BAD_ACCESS / SIGSEGV at 0x8
  startup_manager_run_end                  startup_manager.c:174
  fuse_end                                 fuse.c:982
  fuse_abort                               fuse.c:1002
  -[FuseController application:openFile:]   FuseController.m
  -[NSApplication _doOpenFile:ok:tryTemp:]
  -[NSApplication finishLaunching]