New unsoundness issue in z3str3

[numairmansur]

Hi @mtrberzi,

In the latest commit (41ab578) i get the following incorrect result on the following file:

66.zip

$ ./z3-nightly/bin/z3 smt.string_solver=z3str3 66.smt2 
sat
sat
sat
sat
unsat

Everything should be sat.

Interestingly, in commit 321bad2, i still get a wrong answer but a different one:

$ ./z3-321b/bin/z3 smt.string_solver=z3str3 66.smt2 
sat
sat
unsat
unsat
unsat

[mtrberzi]

This is fixed as of the latest commit (5 SAT responses and all models are valid).