Fix issue 10723

http://d.puremagic.com/issues/show_bug.cgi?id=10723

When except_fillInEHTable() calculates offsets it runs calculation twice in situation when there are struct constructors. Wrong offsets are later used by druntime and program segfaults. 

This is very similar to https://github.com/D-Programming-Language/dmd/pull/1645