Fix a bug in GetOverlappingInputsRangeBinarySearch (#5211)

Summary:
As title.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5211

Differential Revision: D14992018

Pulled By: riversand963

fbshipit-source-id: b5720ea4742029e2fb47ff6d9f8d9de006db4ed4

db/version_set.cc

@@ -2857,7 +2857,7 @@ void VersionStorageInfo::GetOverlappingInputsRangeBinarySearch(
   // If there were no overlapping files, return immediately.
   if (start_index == end_index) {
     if (next_smallest) {
-      next_smallest = nullptr;
+      *next_smallest = nullptr;
     }
     return;
   }