Fix balance calculation issues

[akshaynexus]

Some users report their balance decreasing on each stake,or in some cases increasing drastically on each stake.I havent found a way to reproduce this but needs to be fixed soon.

[akshaynexus]

Ok looks like i got the balance issue on my machine,this is how i got it to give a wrong balance:

• Stake for a while.
• Stop wallet.
• Wait for other wallets to stake/mine.
• Open after while,you would see a wrong balance.