fix: evaluator error

src/scgenerator/evaluator.py

@@ -22,14 +22,22 @@ class ErrorRecord(NamedTuple):
     traceback: str
 
     def pretty_format(self) -> str:
-        return "\n".join(
-            [
-                *(rule.func_name for rule in self.rules_stack[:-1]),
-                self.traceback,
-                self.rules_stack[-1].pretty_format(),
-                str(self.error),
-            ]
-        )
+        if self.rules_stack:
+            return "\n".join(
+                [
+                    *(rule.func_name for rule in self.rules_stack[:-1]),
+                    self.traceback,
+                    self.rules_stack[-1].pretty_format(),
+                    str(self.error),
+                ]
+            )
+        else:
+            return "\n".join(
+                [
+                    self.traceback,
+                    str(self.error),
+                ]
+            )
 
 
 class EvaluatorError(Exception):