Leaving the last two elements uninitialized is mostly harmless since the
shader doesn't actually use them, but the driver might try to do some kind of
analysis on them.

Reported by Marcus Meissner.

This is a follow up of 16ddc624.

Commit 4cf70b14 was causing the tests to
crash.  The reason is due to a Wine bug in NdrPointerUnmarshall().
Windows returns the same pointer (which is later released in a call to
NdrPointerFree()), while Wine makes a copy which Valgrind correctly
spots is leaked.