patch 8.0.0395: testing the + register fails with Motif

Problem:    Testing the + register fails with Motif.
Solution:   Also ignore the "failed to create input context" error in the
            second gvim.  Don't use msg() when it would result in a dialog.

src/message.c

@@ -605,7 +605,8 @@ emsg(char_u *s)
 #ifdef FEAT_EVAL
     /* When testing some errors are turned into a normal message. */
     if (ignore_error(s))
-	return msg(s);
+	/* don't call msg() if it results in a dialog */
+	return msg_use_printf() ? FALSE : msg(s);
 #endif
 
     called_emsg = TRUE;