--- main/channel.c	(Asterisk 13.38.1)
+++ main/channel.c	(working copy)
@@ -6387,4 +6387,9 @@ struct ast_channel *ast_request(const ch
 		tmp_cap = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);
-		if (tmp_cap) {
-			ast_format_cap_append_from_cap(tmp_cap, request_cap, AST_MEDIA_TYPE_AUDIO);
+		if (!tmp_cap) {
+			AST_RWLIST_UNLOCK(&backends);
+			return NULL;
+		}
+
+		ast_format_cap_append_from_cap(tmp_cap, request_cap, AST_MEDIA_TYPE_AUDIO);
+		if (!ast_format_cap_empty(tmp_cap)) {
 			/* We have audio - is it possible to connect the various calls to each other?
@@ -6421,3 +6426,5 @@ struct ast_channel *ast_request(const ch
 		ast_format_cap_remove_by_type(joint_cap, AST_MEDIA_TYPE_AUDIO);
-		ast_format_cap_append(joint_cap, best_audio_fmt, 0);
+		if (best_audio_fmt) { /* text+video call? then, this is NULL */
+			ast_format_cap_append(joint_cap, best_audio_fmt, 0);
+		}