Fix missing istrans() method for TSVI{SVI}

Author: penelopeysm

src/simple_varinfo.jl

@@ -502,6 +502,7 @@ end
 istrans(vi::SimpleVarInfo) = !(vi.transformation isa NoTransformation)
 istrans(vi::SimpleVarInfo, ::VarName) = istrans(vi)
 istrans(vi::ThreadSafeVarInfo{<:SimpleVarInfo}, vn::VarName) = istrans(vi.varinfo, vn)
+istrans(vi::ThreadSafeVarInfo{<:SimpleVarInfo}) = istrans(vi.varinfo)
 
 islinked(vi::SimpleVarInfo) = istrans(vi)