Initialize a variable in ldb to make code analysis tool happy

Summary: Closes https://github.com/facebook/rocksdb/pull/2529

Differential Revision: D5378787

Pulled By: siying

fbshipit-source-id: 801ecacc2804f77cb3c9e5e665829e439db68800

tools/ldb_cmd.cc

@@ -1086,7 +1086,7 @@ CreateColumnFamilyCommand::CreateColumnFamilyCommand(
 }
 
 void CreateColumnFamilyCommand::DoCommand() {
-  ColumnFamilyHandle* new_cf_handle;
+  ColumnFamilyHandle* new_cf_handle = nullptr;
   Status st = db_->CreateColumnFamily(options_, new_cf_name_, &new_cf_handle);
   if (st.ok()) {
     fprintf(stdout, "OK\n");