Adding missing symbol validation to grammar parser.

Author: HanClinto

common/grammar-parser.cpp

@@ -416,8 +416,20 @@ namespace grammar_parser {
     std::vector<const llama_grammar_element *> parse_state::c_rules() {
         std::vector<const llama_grammar_element *> ret;
         ret.reserve(rules.size());
+        unsigned int cnt = 0;
         for (const auto & rule : rules) {
-            ret.push_back(rule.data());
+            // Ensure it's not empty
+            if (rule.data() != nullptr) {
+                ret.push_back(rule.data());
+            } else {
+                // Find the symbol ID for this rule ID
+                for (const auto & kv : symbol_ids) {
+                    if (kv.second == cnt) {
+                        throw std::runtime_error("Undefined rule identifier '" + kv.first + "'");
+                    }
+                }
+            }
+            cnt++;
         }
         return ret;
     }