Fix nullptr dereference in adaptive_table

Summary:
@dulmarod Ran infer on RocksDB and found that we dereference nullptr in adaptive_table
https://fb.facebook.com/groups/rocksdb/permalink/1046374415411173/

Test Plan: make check -j64

Reviewers: sdong, yhchiang, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56973

table/adaptive_table_factory.cc

@@ -78,25 +78,25 @@ std::string AdaptiveTableFactory::GetPrintableTableOptions() const {
   const int kBufferSize = 200;
   char buffer[kBufferSize];
 
-  if (!table_factory_to_write_) {
+  if (table_factory_to_write_) {
     snprintf(buffer, kBufferSize, "  write factory (%s) options:\n%s\n",
              table_factory_to_write_->Name(),
              table_factory_to_write_->GetPrintableTableOptions().c_str());
     ret.append(buffer);
   }
-  if (!plain_table_factory_) {
+  if (plain_table_factory_) {
     snprintf(buffer, kBufferSize, "  %s options:\n%s\n",
              plain_table_factory_->Name(),
              plain_table_factory_->GetPrintableTableOptions().c_str());
     ret.append(buffer);
   }
-  if (!block_based_table_factory_) {
+  if (block_based_table_factory_) {
     snprintf(buffer, kBufferSize, "  %s options:\n%s\n",
              block_based_table_factory_->Name(),
              block_based_table_factory_->GetPrintableTableOptions().c_str());
     ret.append(buffer);
   }
-  if (!cuckoo_table_factory_) {
+  if (cuckoo_table_factory_) {
     snprintf(buffer, kBufferSize, "  %s options:\n%s\n",
              cuckoo_table_factory_->Name(),
              cuckoo_table_factory_->GetPrintableTableOptions().c_str());