Fixing Memory usage with empty size data in VM

[zilm13]

Should fix block 3467853 in Ropsten
Some points:

Over an account’s execution, the total fee for memoryusage
payable is proportional to smallest multiple of 32
bytes that are required such that all memory indices
(whether for read or write) are included in the range. This
is paid for on a just-in-time basis; as such, referencing an
area of memory at least 32 bytes greater than any previously
indexed memory will certainly result in an additional
memory usage fee.

From yellow paper. So, when addressing 0 length part of memory we are not addressing any memory part.