fix: InsertFromFile() and RemoveFromFile() read extra value (#567)

Author: slk000

src/storage/index/b_plus_tree.cpp

@@ -123,9 +123,7 @@ INDEX_TEMPLATE_ARGUMENTS
 void BPLUSTREE_TYPE::InsertFromFile(const std::string &file_name, Transaction *txn) {
   int64_t key;
   std::ifstream input(file_name);
-  while (input) {
-    input >> key;
-
+  while (input >> key) {
     KeyType index_key;
     index_key.SetFromInteger(key);
     RID rid(key);
@@ -140,8 +138,7 @@ INDEX_TEMPLATE_ARGUMENTS
 void BPLUSTREE_TYPE::RemoveFromFile(const std::string &file_name, Transaction *txn) {
   int64_t key;
   std::ifstream input(file_name);
-  while (input) {
-    input >> key;
+  while (input >> key) {
     KeyType index_key;
     index_key.SetFromInteger(key);
     Remove(index_key, txn);