stream: Make ast_stream_topology_create_from_format_cap() allow NULL cap.

Change-Id: Ie29760c49c25d7022ba2124698283181a0dd5d08

include/asterisk/stream.h

@@ -356,7 +356,7 @@ int ast_stream_topology_set_stream(struct ast_stream_topology *topology,
  * creates a topology and separates the media types in format_cap into
  * separate streams.
  *
- * \param caps The format capabilities structure
+ * \param caps The format capabilities structure (NULL creates an empty topology)
  *
  * \retval non-NULL success
  * \retval NULL failure

main/channel_internal_api.c

@@ -852,14 +852,10 @@ void ast_channel_nativeformats_set(struct ast_channel *chan,
 		return;
 	}
 
-	if ((!ast_channel_is_multistream(chan)) || !value) {
+	if (!ast_channel_is_multistream(chan) || !value) {
 		struct ast_stream_topology *new_topology;
 
-		if (!value) {
-			new_topology = ast_stream_topology_alloc();
-		} else {
-			new_topology = ast_stream_topology_create_from_format_cap(value);
-		}
+		new_topology = ast_stream_topology_create_from_format_cap(value);
 		ast_channel_internal_set_stream_topology(chan, new_topology);
 	}
 }

main/stream.c

@@ -345,11 +345,9 @@ struct ast_stream_topology *ast_stream_topology_create_from_format_cap(
 	struct ast_stream_topology *topology;
 	enum ast_media_type type;
 
-	ast_assert(cap != NULL);
-
 	topology = ast_stream_topology_alloc();
-	if (!topology) {
-		return NULL;
+	if (!topology || !cap || !ast_format_cap_count(cap)) {
+		return topology;
 	}
 
 	for (type = AST_MEDIA_TYPE_UNKNOWN + 1; type < AST_MEDIA_TYPE_END; type++) {