[template-glib] eval: fix possible dereference of args_ar

[Christian Hergert <chergert src gnome org>]

commit 377e59b2c15aad43628f3274ced6c5f8d33098d4
Author: Christian Hergert <chergert redhat com>
Date:   Fri May 6 10:16:50 2022 -0700

    eval: fix possible dereference of args_ar

 src/tmpl-expr-eval.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/src/tmpl-expr-eval.c b/src/tmpl-expr-eval.c
index a5244e9..723bca7 100644
--- a/src/tmpl-expr-eval.c
+++ b/src/tmpl-expr-eval.c
@@ -1359,8 +1359,11 @@ tmpl_expr_user_fn_call_eval (TmplExprUserFnCall  *node,
     }
 
   expr = tmpl_symbol_get_expr (symbol, &args_ar);
-  n_args = args_ar != NULL ? args_ar->len : 0;
-  args = (const char * const *)(gpointer)args_ar->pdata;
+
+  if (args_ar == NULL)
+    n_args = 0, args = NULL;
+  else
+    n_args = args_ar->len, args = (const char * const *)(gpointer)args_ar->pdata;
 
 prepare:
   g_assert (expr != NULL);