[Minor] Use empty prompt instead of NULL

Issue: #2591

diff --git a/src/lua/lua_util.c b/src/lua/lua_util.c
index 0e61d6e849ee5b0940abc6341ea596b2560b2698..9ed095c34d22c427b859377a652508aff7c80a2c 100644 (file)
--- a/src/lua/lua_util.c
+++ b/src/lua/lua_util.c
@@ -2458,7 +2458,7 @@ static gint
 lua_util_readline (lua_State *L)
 {
        LUA_TRACE_POINT;
-       const gchar *prompt = NULL;
+       const gchar *prompt = "";
        gchar *input;
 
        if (lua_type (L, 1) == LUA_TSTRING) {