`==` in tables should not raise KeyError
`==` in tables should not raise KeyError

 * With previous code, the compiler deduced that equalsImpl may raise
   a KeyError. While this could only actually happen in a nasty
   multi-threaded environment, I fixed the code so that it will never happen.

jfhg/Nim,dom96/Nim,russpowers/Nim,singularperturbation/Nim,haiodo/Nim,singularperturbation/Nim,haiodo/Nim,haiodo/Nim,haiodo/Nim,haiodo/Nim,mbaulch/Nim,mbaulch/Nim,tulayang/Nim,jfhg/Nim,mbaulch/Nim,jfhg/Nim,tulayang/Nim,jfhg/Nim,dom96/Nim,dom96/Nim,dom96/Nim,russpowers/Nim,singularperturbation/Nim,russpowers/Nim,tulayang/Nim,russpowers/Nim,haiodo/Nim,mbaulch/Nim,dom96/Nim,mbaulch/Nim,russpowers/Nim,singularperturbation/Nim,russpowers/Nim,tulayang/Nim,singularperturbation/Nim,russpowers/Nim,dom96/Nim,jfhg/Nim,dom96/Nim,singularperturbation/Nim,tulayang/Nim,jfhg/Nim,mbaulch/Nim,tulayang/Nim,singularperturbation/Nim,mbaulch/Nim,haiodo/Nim,jfhg/Nim