Assertion failure

[BrunoDutertre]

Hi,

We've seen z3-4.12.4 and 4.12.5 crash on some examples. Here's a reduced problem that
triggers the crash reduced-more.smt2.txt

It produces an assertion failure when z3 is built in debug mode. Here's the trace:

> z3 reduced-more.smt2
ASSERTION VIOLATION
File: ../src/smt/smt_context.h
Line: 1018
l != null_literal
(C)ontinue, (A)bort, (S)top, (T)hrow exception, Invoke (G)DB