Fix some bugs with gatom keyboard grab.

- Dangling #keyname_a binding causing crashes after the gatom got
  freed (possibly because its canvas window was closed while the grab
  was still in progress).

- gatom keyboard input being forwarded to the wrong callback when
  switching to the main window after a glist_grabx. This wasn't an issue
  before, but we now use a callback separate from the object's list
  method, to make listbox work properly (which of course expects real
  list input, not just some random key events, in its list method).

pd/src/g_editor.c

@@ -5669,7 +5669,7 @@ void canvas_key(t_canvas *x, t_symbol *s, int ac, t_atom *av)
     // now broadcast key press to key et al. objects
     // [email protected] 20200918: only do so if we do not have an object
     // that has grabbed the keyboard, such as gatom or iemgui numbox
-    if (!x || !x->gl_editor || !x->gl_editor->e_grab)
+    if (!keynamesym_a->s_thing)
     {
         if (!autorepeat)
         {

pd/src/g_text.c

@@ -1702,6 +1702,9 @@ static void gatom_free(t_gatom *x)
     if (*x->a_symfrom->s_name)
         pd_unbind(&x->a_text.te_pd,
             canvas_realizedollar(x->a_glist, x->a_symfrom));
+    t_symbol *keynamesym_a = gensym("#keyname_a");
+    if (keynamesym_a->s_thing)
+        pd_unbind(&x->a_text.ob_pd, keynamesym_a);
     gfxstub_deleteforkey(x);
 }