miniobject: add gst_clear_mini_object()

This is based on g_clear_object(). Basically, you can use this instead
of using gst_mini_object_unref (which needs to be preceded by a NULL-check).

Also fixes #275

gst/gstminiobject.c

@@ -668,6 +668,30 @@ gst_mini_object_unref (GstMiniObject * mini_object)
   }
 }
 
+/**
+ * gst_clear_mini_object: (skip)
+ * @object_ptr: a pointer to a #GstMiniObject reference
+ *
+ * Clears a reference to a #GstMiniObject.
+ *
+ * @object_ptr must not be %NULL.
+ *
+ * If the reference is %NULL then this function does nothing.
+ * Otherwise, the reference count of the object is decreased using
+ * gst_mini_object_unref() and the pointer is set to %NULL.
+ *
+ * A macro is also included that allows this function to be used without
+ * pointer casts.
+ *
+ * Since: 1.16
+ **/
+#undef gst_clear_mini_object
+void
+gst_clear_mini_object (volatile GstMiniObject ** object_ptr)
+{
+  g_clear_pointer (object_ptr, gst_mini_object_unref);
+}
+
 /**
  * gst_mini_object_replace:
  * @olddata: (inout) (transfer full) (nullable): pointer to a pointer to a

gst/gstminiobject.h

@@ -234,6 +234,10 @@ GstMiniObject * gst_mini_object_ref		(GstMiniObject *mini_object);
 GST_API
 void            gst_mini_object_unref		(GstMiniObject *mini_object);
 
+GST_API
+void        gst_clear_mini_object (volatile GstMiniObject **object_ptr);
+#define     gst_clear_mini_object(object_ptr) g_clear_pointer ((object_ptr), gst_mini_object_unref)
+
 GST_API
 void            gst_mini_object_weak_ref        (GstMiniObject *object,
 					         GstMiniObjectNotify notify,