don't attempt to start input method if path is empty

This allows a user to explicitly disable the input
method by setting path to blank;

Signed-off-by: Murray Calavera <murray.calavera@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/text-backend.c

@@ -920,6 +920,9 @@ launch_input_method(struct text_backend *text_backend)
 	if (!text_backend->input_method.path)
 		return;
 
+	if (strcmp(text_backend->input_method.path, "") == 0)
+		return;
+
 	if (text_backend->input_method.process.pid != 0)
 		return;