Tetra0 test fix (#29)
Tetra0 test fix (#29)

* fix mat.zero() in tetra0_test
dmitryikh/nla3d,SchetininVitaliy/nla3d,dmitryikh/nla3d,dmitryikh/nla3d,SchetininVitaliy/nla3d,SchetininVitaliy/nla3d,SchetininVitaliy/nla3d,dmitryikh/nla3d