Always run the OS X loop even if no windows.

Otherwise this can trigger infinite Python-Icon-In-Dock bouncing.
See  #10137. I will guess that this is because application on OS X may
not have windows and still need to process events.

It may be that an alternative is to run the loop only once the first
time, but I'm unsure.

    at_least_once = False

    def inputhook(context):
	"""Inputhook for Cocoa (NSApp)"""
	NSApp = _NSApp()
	window_count = msg(
	    msg(NSApp, n('windows')),
	    n('count')
	)
	if not window_count and not at_least_once:
	    at_least_once = True
	    return
	_stop_on_read(context.fileno())
	msg(NSApp, n('run'))
	if not _triggered.is_set():
	    # app closed without firing callback,
	    # probably due to last window being closed.
	    # Run the loop manually in this case,
	    # since there may be events still to process (#9734)
	    CoreFoundation.CFRunLoopRun()

Closes  #10137

IPython/terminal/pt_inputhooks/osx.py

@@ -127,12 +127,6 b' def _stop_on_read(fd):'
 def inputhook(context):
     """Inputhook for Cocoa (NSApp)"""
     NSApp = _NSApp()
-    window_count = msg(
-        msg(NSApp, n('windows')),
-        n('count')
-    )
-    if not window_count:
-        return
     _stop_on_read(context.fileno())
     msg(NSApp, n('run'))
     if not _triggered.is_set():