Index: main/pbx.c
===================================================================
--- main/pbx.c	(revision 66979)
+++ main/pbx.c	(working copy)
@@ -2248,10 +2248,12 @@
 	if (e) {
 		if (hint)
 			ast_copy_string(hint, ast_get_extension_app(e), hintsize);
-		if (name) {
+		if (name && namesize) {
 			const char *tmp = ast_get_extension_app_data(e);
 			if (tmp)
 				ast_copy_string(name, tmp, namesize);
+			else
+				*name = '\0';
 		}
 		return -1;
 	}