fix: synchronize access of pWalHandle with mutex in raftLogGetEntry

source/libs/sync/src/syncRaftLog.c

@@ -234,18 +234,17 @@ int32_t raftLogGetEntry(struct SSyncLogStore* pLogStore, SyncIndex index, SSyncR
 
   *ppEntry = NULL;
 
-  // SWalReadHandle* pWalHandle = walOpenReadHandle(pWal);
+  int64_t ts1 = taosGetTimestampNs();
+  taosThreadMutexLock(&(pData->mutex));
+
   SWalReader* pWalHandle = pData->pWalHandle;
   if (pWalHandle == NULL) {
     terrno = TSDB_CODE_SYN_INTERNAL_ERROR;
     sError("vgId:%d, wal handle is NULL", pData->pSyncNode->vgId);
-
+    taosThreadMutexUnlock(&(pData->mutex));
     return -1;
   }
 
-  int64_t ts1 = taosGetTimestampNs();
-  taosThreadMutexLock(&(pData->mutex));
-
   int64_t ts2 = taosGetTimestampNs();
   code = walReadVer(pWalHandle, index);
   int64_t ts3 = taosGetTimestampNs();