rescue: initialize CLEANUP pointer variable

This way it will not try to free uninitialized memory when going out of
scope, and the inspector mode is not enabled.

Fixes commit 3637c42f4e.

rescue/escape.c

@@ -236,7 +236,7 @@ print_help (void)
 static void
 print_inspector (void)
 {
-  CLEANUP_FREE_STRING_LIST char **roots;
+  CLEANUP_FREE_STRING_LIST char **roots = NULL;
   size_t i;
   const char *root;
   char *str;