`--compare_runs` now segfaults

Comparing results from --save_run with --compare_runs worked fine before, but now it leads to segmentation faults.

$  ./goblint -v --compare_runs out/coreutils/cksum_comb.c.always-side_widen out/coreutils/cksum_comb.c.cycle-side_widen coreutils/cksum_comb.c
...
Unmarshalling out/coreutils/cksum_comb.c.always-side_widen/solver.marshalled... If type of content changed, this will result in a segmentation fault!
Unmarshalling out/coreutils/cksum_comb.c.cycle-side_widen/solver.marshalled... If type of content changed, this will result in a segmentation fault!
[1]    19594 segmentation fault (core dumped)  ./goblint -v --compare_runs out/coreutils/cksum_comb.c.always-side_widen   2>

Runs have been analyzed directly before with the same binary.

$ ./goblint -v coreutils/cksum_comb.c --sets exp.solver.td3.side_widen always --enable exp.earlyglobs --enable ana.int.interval --disable ana.int.enums --disable ana.int.def_exc --disable exp.full-context --disable exp.widen-context --disable exp.widen-context-partial --sets exp.privatization none --disable exp.solver.td3.space_restore --sets dbg.timeout 8h --sets save_run out/coreutils/cksum_comb.c.always-side_widen
...
$ ./goblint -v coreutils/cksum_comb.c --sets exp.solver.td3.side_widen cycle --enable exp.earlyglobs --enable ana.int.interval --disable ana.int.enums --disable ana.int.def_exc --disable exp.full-context --disable exp.widen-context --disable exp.widen-context-partial --sets exp.privatization none --disable exp.solver.td3.space_restore --sets dbg.timeout 8h --sets save_run out/coreutils/cksum_comb.c.cycle-side_widen
...

There's not much that should be going on and the code for comparing did not change:

https://github.com/goblint/analyzer/blob/201b7d94f8269799f4f2f7dc267ec95e48368ff9/src/framework/control.ml#L403-L410

https://github.com/goblint/analyzer/blob/201b7d94f8269799f4f2f7dc267ec95e48368ff9/src/framework/constraints.ml#L1166-L1180

Reproduce the crash with the shown --save_run and --compare_runs commands, then inspect src/framework/control.ml lines 403-410 and src/framework/constraints.ml lines 1166-1180. Compare the unmarshalling and comparison paths for runs produced by the same binary. Done means comparing the two saved runs completes without a segmentation fault.