Fix error with fn key in NS port (bug#44533)

* src/nsterm.m ([EmacsView keyDown:]): Move the correction for fn key
handling to before the modifiers are calculated.

(cherry picked from commit 7970610d48)

src/nsterm.m

@@ -6350,6 +6350,14 @@ flag set (this is probably a bug in the OS).  */
             code = 0xFF08; /* backspace */
           else
             code = fnKeysym;
+
+          /* Function keys (such as the F-keys, arrow keys, etc.) set
+             modifiers as though the fn key has been pressed when it
+             hasn't.  Also some combinations of fn and a function key
+             return a different key than was pressed (e.g. fn-<left>
+             gives <home>).  We need to unset the fn key flag in these
+             cases.  */
+          flags &= ~NS_FUNCTION_KEY_MASK;
         }
 
       /* The ⌘ and ⌥ modifiers can be either shift-like (for alternate
@@ -6371,17 +6379,6 @@ In that case we use UCKeyTranslate (ns_get_shifted_character)
       Lisp_Object kind = fnKeysym ? QCfunction : QCordinary;
       emacs_event->modifiers = EV_MODIFIERS2 (flags, kind);
 
-      /* Function keys (such as the F-keys, arrow keys, etc.) set
-         modifiers as though the fn key has been pressed when it
-         hasn't.  Also some combinations of fn and a function key
-         return a different key than was pressed (e.g. fn-<left> gives
-         <home>).  We need to unset the fn modifier in these cases.
-         FIXME: Can we avoid setting it in the first place?  */
-      if (fnKeysym && (flags & NS_FUNCTION_KEY_MASK))
-        emacs_event->modifiers
-          ^= parse_solitary_modifier (mod_of_kind (ns_function_modifier,
-                                                   QCfunction));
-
       if (NS_KEYLOG)
         fprintf (stderr, "keyDown: code =%x\tfnKey =%x\tflags = %x\tmods = %x\n",
                  code, fnKeysym, flags, emacs_event->modifiers);