Reject corpus which produces empty range for LALRPOP parser (#10876)

## Summary

This PR updates the `ruff_new_parser_equiv` fuzzer target to reject the
corpus which produces an empty range for the AST from LALRPOP. If there
are no nodes, then LALRPOP produces an empty range while the new parser
uses the correct range of the source itself.

fuzz/fuzz_targets/ruff_new_parser_equiv.rs

@@ -20,16 +20,27 @@ fn do_fuzz(case: &[u8]) -> Corpus {
         return Corpus::Keep; // keep even rejected source code as this may allow us to explore later
     };
 
-    set_new_parser(true);
-    let module_new = parse_tokens(tokens.clone(), source, source_type.as_mode());
-
     set_new_parser(false);
-    let module_lalrpop = parse_tokens(tokens, source, source_type.as_mode());
+    let result_lalrpop = parse_tokens(tokens.clone(), source, source_type.as_mode());
+
+    if result_lalrpop.as_ref().is_ok_and(|ast_lalrpop| {
+        ast_lalrpop
+            .as_module()
+            .is_some_and(|module_lalrpop| module_lalrpop.range.is_empty())
+    }) {
+        // Reject the corpus which only contains whitespaces, comments, and newlines. This is
+        // because the module range produced by LALRPOP is empty while it is the source length in
+        // case of the new parser.
+        return Corpus::Reject;
+    }
+
+    set_new_parser(true);
+    let result_new = parse_tokens(tokens, source, source_type.as_mode());
 
-    assert_eq!(module_lalrpop.is_ok(), module_new.is_ok());
+    assert_eq!(result_lalrpop.is_ok(), result_new.is_ok());
 
-    if let (Ok(module_lalrpop), Ok(module_new)) = (module_lalrpop, module_new) {
-        assert_eq!(module_lalrpop, module_new);
+    if let (Ok(ast_lalrpop), Ok(ast_new)) = (result_lalrpop, result_new) {
+        assert_eq!(ast_lalrpop, ast_new);
     }
 
     Corpus::Keep