Incorrect order in reward function chops small mint rewards

I started forum thread http://www.peercointalk.org/index.php?topic=2638.0 on this issue. First, I observed that very small rewards are rounded to 0 on testnet, while their coinage is probably consumed. If I understand this correctly, the rounding error is caused by incorrect order in multiplication and integer division. I send suggested fix here. _I am, however, not sure, if my correction could cause overflow_, can you please check it?