Make an invalid addrIncoming so that old clients crash.

This prevents old clients from opening, and thus corrupting
or otherwise causing harm to encrypted wallets.

src/main.cpp

@@ -55,7 +55,6 @@ int64 nHPSTimerStart;
 // Settings
 int fGenerateBitcoins = false;
 int64 nTransactionFee = 0;
-CAddress addrIncoming;
 int fLimitProcessors = false;
 int nLimitProcessors = 1;
 int fMinimizeToTray = true;