[rhythmbox] xfade: check if a probe has been added before removing it

[Jonathan Matthew <jmatthew src gnome org>]

commit 24ac42b11ab7f3bbf57325f71bdd34b9a3815079
Author: Jonathan Matthew <jonathan d14n org>
Date:   Thu Apr 27 08:22:48 2017 +1000

    xfade: check if a probe has been added before removing it

 backends/gstreamer/rb-player-gst-xfade.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/backends/gstreamer/rb-player-gst-xfade.c b/backends/gstreamer/rb-player-gst-xfade.c
index cac4edf..d553397 100644
--- a/backends/gstreamer/rb-player-gst-xfade.c
+++ b/backends/gstreamer/rb-player-gst-xfade.c
@@ -1131,8 +1131,10 @@ link_and_unblock_stream (RBXFadeStream *stream, GError **error)
        if (stream->src_blocked) {
                GstStateChangeReturn state_ret;
 
-               gst_pad_remove_probe (stream->src_pad, stream->block_probe_id);
-               stream->block_probe_id = 0;
+               if (stream->block_probe_id != 0) {
+                       gst_pad_remove_probe (stream->src_pad, stream->block_probe_id);
+                       stream->block_probe_id = 0;
+               }
 
                rb_debug ("stream %s is unblocked -> FADING_IN | PLAYING", stream->uri);
                stream->src_blocked = FALSE;