cuda: Fix GstCudaContext refcount bug

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2334>

subprojects/gst-plugins-bad/gst-libs/gst/cuda/gstcudautils.c

@@ -236,6 +236,7 @@ gst_cuda_ensure_element_context (GstElement * element, gint device_id,
         context, *cuda_ctx);
     msg = gst_message_new_have_context (GST_OBJECT_CAST (element), context);
     gst_element_post_message (GST_ELEMENT_CAST (element), msg);
+    gst_context_unref (context);
   }
 
   return TRUE;