Create an empty structure to pass to gst_message_new_application if we don't have a valid one.

When passed a NULL structure gst_message_new_application fails with
the following error.  GStreamer-CRITICAL **:
gst_message_new_application: assertion 'structure != NULL' failed

1 files changed, 1 insertions, 1 deletions

diff --git a/src/QGst/message.cpp b/src/QGst/message.cpp
index a252562..3e7bb56 100644
--- a/src/QGst/message.cpp
+++ b/src/QGst/message.cpp
@@ -348,7 +348,7 @@ void StreamStatusMessage::setStreamStatusObject(const QGlib::Value & obj)
 
 ApplicationMessagePtr ApplicationMessage::create(const ObjectPtr & source, const Structure & structure)
 {
-    GstStructure *s = structure.isValid() ? gst_structure_copy(structure) : NULL;
+    GstStructure *s = structure.isValid() ? gst_structure_copy(structure) : gst_structure_new_empty("null");
     return ApplicationMessagePtr::wrap(gst_message_new_application(source, s), false);
 }