Fix clang_analyze error (#7777)

Summary:
Fix clang_analyze error

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7777

Test Plan:
USE_CLANG=1 TEST_TMPDIR=/dev/shm/rocksdb OPT=-g make -j64
analyze

Reviewed By: jay-zhuang

Differential Revision: D25601675

Pulled By: akankshamahajan15

fbshipit-source-id: 30f58cf4d575a2d546c455fb43e856455eb72a07

utilities/transactions/transaction_test.cc

@@ -5893,6 +5893,7 @@ TEST_P(TransactionTest, DuplicateKeys) {
     std::vector<ColumnFamilyHandle*> handles;
     ASSERT_OK(ReOpenNoDelete(cfds, &handles));
 
+    assert(db != nullptr);
     ASSERT_OK(db->Put(write_options, "foo0", "init"));
     ASSERT_OK(db->Put(write_options, "foo1", "init"));
     ASSERT_OK(db->Put(write_options, handles[1], "foo0", "init"));
@@ -6194,6 +6195,7 @@ TEST_P(TransactionTest, DoubleCrashInRecovery) {
       column_families.push_back(
           ColumnFamilyDescriptor("two", ColumnFamilyOptions()));
       ASSERT_OK(ReOpenNoDelete(column_families, &handles));
+      assert(db != nullptr);
 
       if (write_after_recovery) {
         // Write data to the log right after the corrupted log