Bug 346001

If you try to enter a transaction into an investment account that has a zero total for the fees the enter button is disabled.
I have to pay a quarterly fee which becomes a "Commission Credit" so, for each trade I make, a commission deduction should be made until there is no credit left at which point it should be deducted as a fee from the trade.
If I try to set up the fee as a split transaction, going to an expense category and a full/partial reversal in the commission account, zero total fees are not allowed.

Reproducible: Always

Steps to Reproduce:
1. Create an expense category for fees
2. Create an account for commission credits
3. Create a buy transaction with a fee and use the split functionality to have an expense of 1.50 and a reversal into the commission credits account of 1.50 so that the split total is zero.

Actual Results:  
1. Enter button is disabled.

Expected Results:  
1. Enter button is enabled and you can enter a transaction.