[gn] Enable stricter build flags

src/extensions/statistics-extension.cc

Index: src/extensions/statistics-extension.cc
diff --git a/src/extensions/statistics-extension.cc b/src/extensions/statistics-extension.cc
index ad412975cf489e4b62eb68ed3cd73825e8a19cff..3e49c527e30028035e096555446fcebb2a54aaf8 100644
--- a/src/extensions/statistics-extension.cc
+++ b/src/extensions/statistics-extension.cc
@@ -144,7 +144,7 @@ void StatisticsExtension::GetCounters(
   HeapObject* obj;
   int reloc_info_total = 0;
   int source_position_table_total = 0;
-  while ((obj = iterator.next())) {
+  while ((obj = iterator.next()) != nullptr) {
     if (obj->IsCode()) {
       Code* code = Code::cast(obj);
       reloc_info_total += code->relocation_info()->Size();