make tfragment_gc more robust
make tfragment_gc more robust

dom96/Nim,dom96/Nim,dom96/Nim,russpowers/Nim,russpowers/Nim,dom96/Nim,russpowers/Nim,dom96/Nim,dom96/Nim,russpowers/Nim,russpowers/Nim,russpowers/Nim,russpowers/Nim,dom96/Nim