tools: gst-launch: don't try to remove already-removed GSource from main loop

It's considered a programming error in recent GLib versions now.
We may already have removed the source by returning FALSE from
the callback if it was fired. Fixes warning with newer GLibs
when interrupting a pipeline with Control-C.

tools/gst-launch.c

@@ -460,6 +460,10 @@ print_toc_entry (gpointer data, gpointer user_data)
   g_list_foreach (subentries, print_toc_entry, GUINT_TO_POINTER (indent));
 }
 
+#ifdef G_OS_UNIX
+static guint signal_watch_id;
+#endif
+
 #ifdef G_OS_UNIX
 /* As the interrupt handler is dispatched from GMainContext as a GSourceFunc
  * handler, we can react to this by posting a message. */
@@ -477,6 +481,7 @@ intr_handler (gpointer user_data)
               "message", G_TYPE_STRING, "Pipeline interrupted", NULL)));
 
   /* remove signal handler */
+  signal_watch_id = 0;
   return FALSE;
 }
 
@@ -489,9 +494,6 @@ static EventLoopResult
 event_loop (GstElement * pipeline, gboolean blocking, gboolean do_progress,
     GstState target_state)
 {
-#ifdef G_OS_UNIX
-  guint signal_watch_id;
-#endif
   GstBus *bus;
   GstMessage *message = NULL;
   EventLoopResult res = ELR_NO_ERROR;
@@ -826,7 +828,8 @@ exit:
       gst_message_unref (message);
     gst_object_unref (bus);
 #ifdef G_OS_UNIX
-    g_source_remove (signal_watch_id);
+    if (signal_watch_id > 0)
+      g_source_remove (signal_watch_id);
 #endif
     return res;
   }