Do not require zero features to have zero bits, but do ignore them.
Do not require zero features to have zero bits, but do ignore them.

During database building, zero features may have other bits.  For now,
ignore the fact that zero features have non-zero bits.

Signed-off-by: Keith Rothman <1bc19627a439baf17510dc2d0b2d250c96d445a5@users.noreply.github.com>

SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray