[fix](reader) Fix tracing file reader nullptr issue in push handler.

Author: kaka11chen

be/src/olap/push_handler.cpp

@@ -411,8 +411,10 @@ Status PushBrokerReader::init() {
     _runtime_profile->set_name("PushBrokerReader");
 
     _file_cache_statistics.reset(new io::FileCacheStatistics());
+    _file_reader_stats.reset(new io::FileReaderStats());
     _io_ctx.reset(new io::IOContext());
     _io_ctx->file_cache_stats = _file_cache_statistics.get();
+    _io_ctx->file_reader_stats = _file_reader_stats.get();
     _io_ctx->query_id = &_runtime_state->query_id();
 
     auto slot_descs = desc_tbl->get_tuple_descriptor(0)->slots();

be/src/olap/push_handler.h

@@ -136,6 +136,7 @@ class PushBrokerReader {
     std::vector<TFileRangeDesc> _file_ranges;
 
     std::unique_ptr<io::FileCacheStatistics> _file_cache_statistics;
+    std::unique_ptr<io::FileReaderStats> _file_reader_stats;
     std::unique_ptr<io::IOContext> _io_ctx;
 
     // col names from _slot_descs