Fix ecmul_0-3_5616_28000_96

[s1na]

This PR fixes the failing ecmul_0-3_5616_28000_96 test case. You might notice that the fix is not done in code, but in the test suite. I noticed that the tx is not being executed at all, because the tx sender doesn't have enough balance, but I was puzzled why then this invalid test is failing. I found an explanation in PegaSysEng/pantheon#106. Here's a summary:

A requirement of the test harness is that if a test is invalid and the coinbase account is empty, it should be dropped from the state. This is mainly for state tests, as in blockchain tests, an invalid tx is simply rejected.

It might be a good idea to verify this nevertheless.

[holgerd77]

Think this is a good fix with enough validation for now, further digging would require too much extra work and this won't get lost since it is well documented in the test suite code, will approve.