Fix NPE when broadcast dtl channel can't allocate buffer

src/sql/dtl/ob_dtl_channel_agent.cpp

@@ -350,7 +350,7 @@ int ObDtlChanAgent::switch_buffer(int64_t need_size)
   if (OB_SUCC(ret)) {
     current_buffer_->set_bcast();
     dtl_buf_encoder_.set_new_buffer(current_buffer_);
-  } else {
+  } else if (nullptr != current_buffer_) {
     dtl_buf_allocator_.free_buf(*bcast_ch, current_buffer_);
   }
 

src/sql/dtl/ob_dtl_flow_control.cpp

@@ -59,7 +59,7 @@ int ObDtlFlowControl::init(uint64_t tenant_id, int64_t chan_cnt)
   } else {
     ObTenantConfigGuard tenant_config(TENANT_CONF(tenant_id));
     if (tenant_config.is_valid() && true == tenant_config->_px_message_compression) {
-      compressor_type_ = ObCompressorType::STREAM_LZ4_COMPRESSOR;
+      compressor_type_ = ObCompressorType::LZ4_COMPRESSOR;
     }
     is_init_ = true;
     tenant_id_ = tenant_id;