obtain cs_wallet mutex to protect vchDefaultKey

src/wallet.cpp

@@ -1280,6 +1280,8 @@ bool CWallet::GetKeyFromPool(vector<unsigned char>& result, bool fAllowReuse)
 {
     int64 nIndex = 0;
     CKeyPool keypool;
+    CRITICAL_BLOCK(cs_wallet)
+    {
         ReserveKeyFromKeyPool(nIndex, keypool);
         if (nIndex == -1)
         {
@@ -1294,6 +1296,7 @@ bool CWallet::GetKeyFromPool(vector<unsigned char>& result, bool fAllowReuse)
         }
         KeepKey(nIndex);
         result = keypool.vchPubKey;
+    }
     return true;
 }