Skip DumpStats() on dropped CF (#13900)

Summary:
**Context/Summary:**

DumpStats() do not skip dropped CF and can run into a seg fault like below
```
2025-08-23T06:44:05.0469230Z �[0;32m[ RUN      ] �[mFormatLatest/ColumnFamilyTest.LiveIteratorWithDroppedColumnFamily/0
2025-08-23T06:44:05.0470050Z Received signal 11 (Segmentation fault: 11)
2025-08-23T06:44:05.0470510Z #0   0x7000069305e0
2025-08-23T06:44:05.0471070Z #1   rocksdb::DBImpl::DumpStats() (in librocksdb.10.6.0.dylib) (db_impl.cc:1076)
```

This PR skipped it.

Pull Request resolved: #13900

Test Plan:
- Deterministically repro-ed the seg fault before the fix and ensure it doesn't happen after the fix
```
 diff --git a/db/column_family_test.cc b/db/column_family_test.cc
index 3a2ca06..f57d6f757 100644
 --- a/db/column_family_test.cc
+++ b/db/column_family_test.cc
@@ -2372,11 +2372,17 @@ TEST_P(ColumnFamilyTest, LiveIteratorWithDroppedColumnFamily) {
   int kKeysNum = 10000;
   PutRandomData(1, kKeysNum, 100);
   {
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->LoadDependency(
+        {{"PostDrop", "BeforeAccessCFD"}, {"PostAccessCFD", "BeforeGo"}});
+
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
     std::unique_ptr<Iterator> iterator(
         db_->NewIterator(ReadOptions(), handles_[1]));
     iterator->SeekToFirst();

     DropColumnFamilies({1});
+    TEST_SYNC_POINT("PostDrop");
+    TEST_SYNC_POINT("BeforeGo");

     // Make sure iterator created can still be used.
     int count = 0;
@@ -2386,6 +2392,9 @@ TEST_P(ColumnFamilyTest, LiveIteratorWithDroppedColumnFamily) {
     }
     ASSERT_OK(iterator->status());
     ASSERT_EQ(count, kKeysNum);
+
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->DisableProcessing();
+    ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->ClearAllCallBacks();
   }

   Reopen();
 diff --git a/db/db_impl/db_impl.cc b/db/db_impl/db_impl.cc
index a8e4f5f..a8a0499c0 100644
 --- a/db/db_impl/db_impl.cc
+++ b/db/db_impl/db_impl.cc
@@ -1073,8 +1073,10 @@ void DBImpl::DumpStats() {
         continue;
       }

-      auto* table_factory =
-          cfd->GetCurrentMutableCFOptions().table_factory.get();
+      TEST_SYNC_POINT("BeforeAccessCFD");
+      auto moptions = cfd->GetCurrentMutableCFOptions();
+      auto* table_factory = moptions.table_factory.get();
+      TEST_SYNC_POINT("PostAccessCFD");
       assert(table_factory != nullptr);
       // FIXME: need to a shared_ptr if/when block_cache is going to be mutable
       Cache* cache =
~
```

Reviewed By: archang19

Differential Revision: D81003739

Pulled By: hx235

fbshipit-source-id: bdf3c4cc45988f43e79ebc191a20af5b70ac289f

Author: hx235

db/db_impl/db_impl.cc

@@ -1069,7 +1069,7 @@ void DBImpl::DumpStats() {
   {
     InstrumentedMutexLock l(&mutex_);
     for (auto cfd : versions_->GetRefedColumnFamilySet()) {
-      if (!cfd->initialized()) {
+      if (!cfd->initialized() || cfd->IsDropped()) {
         continue;
       }