additional sanity check in free_string_array

src/cats_strings/cats_strings.c

@@ -160,7 +160,7 @@ struct string_array *copy_string_array(const struct string_array *src)
 
 void free_string_array(struct string_array **array)
 {
-        if (array == NULL) return;
+        if (array == NULL || *array == NULL) return;
 
         struct string_array *this = *array;
         DBG_STRING(log_message(LOG_RAW, "%s: address:        %p\n", __func__, this);)