fix unset catched exception in varEnv
fix unset catched exception in varEnv

bleis-tift/FSharp.Quotations.Compiler,bleis-tift/FSharp.Quotations.Compiler,colinbull/FSharp.Quotations.Compiler,colinbull/FSharp.Quotations.Compiler,pocketberserker/FSharp.Quotations.Compiler,pocketberserker/FSharp.Quotations.Compiler