clang-tidy: Fix readability-redundant-string-init in headers

See https://clang.llvm.org/extra/clang-tidy/checks/readability/redundant-string-init.html

Author: hebasto

src/qt/transactionrecord.h

@@ -76,12 +76,12 @@ class TransactionRecord
     static const int RecommendedNumConfirmations = 6;
 
     TransactionRecord():
-            hash(), time(0), type(Other), address(""), debit(0), credit(0), idx(0)
+            hash(), time(0), type(Other), debit(0), credit(0), idx(0)
     {
     }
 
     TransactionRecord(uint256 _hash, qint64 _time):
-            hash(_hash), time(_time), type(Other), address(""), debit(0),
+            hash(_hash), time(_time), type(Other), debit(0),
             credit(0), idx(0)
     {
     }