fix crash on reset

fix tests

apps/openmw/mwworld/worldmodel.cpp

@@ -92,6 +92,7 @@ void MWWorld::WorldModel::clear()
     mLastGeneratedRefnum = ESM::RefNum{};
     mInteriors.clear();
     mExteriors.clear();
+    mCells.clear();
     std::fill(mIdCache.begin(), mIdCache.end(), std::make_pair(ESM::RefId(), (MWWorld::CellStore*)nullptr));
     mIdCacheIndex = 0;
 }

apps/openmw_test_suite/mwworld/test_store.cpp

@@ -491,9 +491,6 @@ namespace
             else
                 result = esmStore.get<RecordType>().search(refId);
 
-            if (result == nullptr || result->mId != refId)
-                int debug = 0;
-
             ASSERT_NE(result, nullptr);
             EXPECT_EQ(result->mId, refId);
         }