[calls] sip: media-pipeline: Initialize GStreamer if it's not already initialized

[Evangelos Ribeiro Tzaras <devrtz src gnome org>]

commit 92c8a69e17612bb6f996a1e245b59c6e21a9aac9
Author: Evangelos Ribeiro Tzaras <devrtz fortysixandtwo eu>
Date:   Tue Mar 1 12:51:11 2022 +0100

    sip: media-pipeline: Initialize GStreamer if it's not already initialized

 plugins/sip/calls-sip-media-pipeline.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/plugins/sip/calls-sip-media-pipeline.c b/plugins/sip/calls-sip-media-pipeline.c
index 864e6e97..bf4b4cb5 100644
--- a/plugins/sip/calls-sip-media-pipeline.c
+++ b/plugins/sip/calls-sip-media-pipeline.c
@@ -349,6 +349,8 @@ calls_sip_media_pipeline_class_init (CallsSipMediaPipelineClass *klass)
 static void
 calls_sip_media_pipeline_init (CallsSipMediaPipeline *self)
 {
+  if (!gst_is_initialized ())
+    gst_init (NULL, NULL);
 }