Fix bugs in PygletTextView_Implementation and CocoaAlternateEventLoop

[deceitfulsteve]

Here are two small bugfixes to Cocoa-related code, in separate commits.

• The fix for the first one follows some changes in Various MacOSX improvements and fixes #790. While the fix is fairly small, I have included reproduction steps much further down for completeness.
• The second issue occurred while running python -m pyglet.info to file an Issue. I assume the AttributeError, as seen below, is caused by calling CocoaAlternateEventLoop.exit() before CocoaAlternateEventLoop.run().

Traceback (most recent call last):
  File "/Users/steve/git/pyglet/pyglet/info.py", line 178, in _try_dump
    func()
  File "/Users/steve/git/pyglet/pyglet/info.py", line 79, in dump_window
    window.close()
  File "/Users/steve/git/pyglet/pyglet/window/cocoa/__init__.py", line 244, in close
    super(CocoaWindow, self).close()
  File "/Users/steve/git/pyglet/pyglet/window/__init__.py", line 666, in close
    app.event_loop.dispatch_event('on_window_close', self)
  File "/Users/steve/git/pyglet/pyglet/event.py", line 392, in dispatch_event
    raise e
  File "/Users/steve/git/pyglet/pyglet/event.py", line 387, in dispatch_event
    if getattr(self, event_type)(*args):
  File "/Users/steve/git/pyglet/pyglet/app/base.py", line 286, in on_window_close
    self.exit()
  File "/Users/steve/git/pyglet/pyglet/app/cocoa.py", line 112, in exit
    self.platform_event_loop.notify()
AttributeError: 'CocoaAlternateEventLoop' object has no attribute 'platform_event_loop'

Since I skipped opening an issue:

System Information:
truncated python -m pyglet.info

❯ python -m pyglet.info
Platform
------------------------------------------------------------------------------
platform:  macOS-13.6.3-arm64-arm-64bit
release:   22.6.0
machine:   arm64

Python
------------------------------------------------------------------------------
implementation: CPython
sys.version: 3.10.11 (main, May 19 2023, 20:26:42) [Clang 14.0.3 (clang-1403.0.22.14.1)]
sys.maxint: 9223372036854775807
objc.__version__: 10.1
os.getcwd(): /Users/steve/git/pyglet

pyglet
------------------------------------------------------------------------------
pyglet.version: 2.0.12

How To Reproduce
Run this and click the button in the window that pops up.

import pyrender
from PySide6.QtWidgets import QApplication, QPushButton


def render():
    pyrender.OffscreenRenderer(400, 400)


app = QApplication()

button = QPushButton("Press Me!")
button.clicked.connect(render)
button.show()

app.exec()

The resulting traceback should look like:

Exception ignored on calling ctypes callback function: <function ObjCSubclass.method.<locals>.decorator.<locals>.objc_method at 0x11f0c43a0>
Traceback (most recent call last):
  File "/Users/steve/git/pyglet/pyglet/libs/darwin/cocoapy/runtime.py", line 1251, in objc_method
    result = f(py_self, *args)
  File "/Users/steve/git/pyglet/pyglet/window/cocoa/pyglet_textview.py", line 30, in dealloc
    self.empty_string.release()
AttributeError: 'int' object has no attribute 'release'

[caffeinepills]

I think this looks good. If the CFRelease works without error, then we should be in a good spot. Thanks!