heap-use-after-free at ast.h:507

[rainoftime]

Hi, for the following formula

(declare-fun x6 () Bool)
(assert (forall ((x2 Bool)) (let (($x538 (and x6 (not x2)))))))
(check-sat)

z3 be38b25

=138864==ERROR: AddressSanitizer: heap-use-after-free on address 0x60700002e718 at pc 0x0000007c1ef5 bp 0x7ffe3cdfdc10 sp 0x7ffe3cdfdc08
READ of size 8 at 0x60700002e718 thread T0
    #0 0x7c1ef4 in ast::reset_mark1(void*) /home/z3-debug/build/../src/ast/ast.h:507:38
    #1 0x7c1daf in ast_fast_mark<1u>::reset_mark(ast*) /home/z3-debug/build/../src/ast/ast.h:2467:13
    #2 0x7c1ca7 in ast_fast_mark<1u>::reset() /home/z3-debug/build/../src/ast/ast.h:2488:36
    #3 0x7a8e5b in ast_fast_mark<1u>::~ast_fast_mark() /home/z3-debug/build/../src/ast/ast.h:2462:9
    #4 0x4067c04 in flatten_or(ref_vector<expr, ast_manager>&) /home/z3-debug/build/../src/ast/ast_util.cpp:369:1
    #5 0x4067da8 in flatten_or(expr*, ref_vector<expr, ast_manager>&) /home/z3-debug/build/../src/ast/ast_util.cpp:375:5
    #6 0x1274a96 in qe_lite::impl::operator()(uint_set const&, bool, obj_ref<expr, ast_manager>&)