Don't attempt to create a dummy fsspec if the user cancelled out, just
return None.

For now, if the user asks for TEXT files files without type are also
accepted. But it is time to phase out StandardGetFile and friends, really.
diff --git a/Mac/Lib/macfsn.py b/Mac/Lib/macfsn.py
index e7eeacd..8f3203c 100644
--- a/Mac/Lib/macfsn.py
+++ b/Mac/Lib/macfsn.py
@@ -12,6 +12,9 @@
 _movablemodal = 1
 
 def _mktypelist(typelist):
+	# Workaround for OSX typeless files:
+	if 'TEXT' in typelist and not '\0\0\0\0' in typelist:
+		typelist = typelist + ('\0\0\0\0',)
 	if not typelist:
 		return None
 	data = 'Pyth' + struct.pack("hh", 0, len(typelist))
@@ -44,7 +47,7 @@
 		if arg[0] != -128: # userCancelledErr
 			raise Nav.error, arg
 		good = 0
-		fss = macfs.FSSpec(':cancelled')
+		fss = None
 	else:
 		if rr.selection:
 			fss = rr.selection[0]
@@ -74,7 +77,7 @@
 		if arg[0] != -128: # userCancelledErr
 			raise Nav.error, arg
 		good = 0
-		fss = macfs.FSSpec(':cancelled')
+		fss = None
 	else:
 		fss = rr.selection[0]
 	return fss, good
@@ -115,7 +118,7 @@
 		if arg[0] != -128: # userCancelledErr
 			raise Nav.error, arg
 		good = 0
-		fss = macfs.FSSpec(':cancelled')
+		fss = None
 	else:
 		fss = rr.selection[0]
 	return fss, good