imcontextsimple: ensure W32 code only runs on W32 displays

gdk_win32_keymap_check_compose() shouldn't be called for
non-W32 displays (i.e. when using broadway or other backends
that could be made to run on Windows).

gtk/gtkimcontextsimple.c

@@ -1238,6 +1238,8 @@ gtk_im_context_simple_filter_keypress (GtkIMContext *context,
       gboolean success = FALSE;
 
 #ifdef GDK_WINDOWING_WIN32
+      if (GDK_IS_WIN32_DISPLAY (display))
+        {
           guint16  output[2];
           gsize    output_size = 2;
 
@@ -1261,6 +1263,7 @@ gtk_im_context_simple_filter_keypress (GtkIMContext *context,
             case GDK_WIN32_KEYMAP_MATCH_INCOMPLETE:
               return TRUE;
             }
+        }
 #endif
 
       G_LOCK (global_tables);