CWallet: fix nTimeFirstKey init, by making constructor init common code

Don't repeat yourself etc.

src/wallet.h

@@ -142,6 +142,17 @@ public:
     unsigned int nMasterKeyMaxID;
 
     CWallet()
+    {
+        SetNull();
+    }
+    CWallet(std::string strWalletFileIn)
+    {
+        SetNull();
+
+        strWalletFile = strWalletFileIn;
+        fFileBacked = true;
+    }
+    void SetNull()
     {
         nWalletVersion = FEATURE_BASE;
         nWalletMaxVersion = FEATURE_BASE;
@@ -153,18 +164,6 @@ public:
         nLastResend = 0;
         nTimeFirstKey = 0;
     }
-    CWallet(std::string strWalletFileIn)
-    {
-        nWalletVersion = FEATURE_BASE;
-        nWalletMaxVersion = FEATURE_BASE;
-        strWalletFile = strWalletFileIn;
-        fFileBacked = true;
-        nMasterKeyMaxID = 0;
-        pwalletdbEncryption = NULL;
-        nOrderPosNext = 0;
-        nNextResend = 0;
-        nLastResend = 0;
-    }
 
     std::map<uint256, CWalletTx> mapWallet;