Suggest replacing these two lines with:
```
        if (op == OPcolon)
            assert(e1 && e2);
```
Suggest inserting this code before line 4947:
```
                    assert(e2->Eoper == OPcolon || e2->Eoper == OPcolon2);
                    elem *e21 = e2->E1 = optelem(e2->E1, goal);
                    elem *e22 = e2->E2 = optelem(e2->E2, goal);
                    if (!e21)
                    {   if (!e22)
                        {
                            e = el_selecte1(e);
                            goto beg;
                        }
                        // Rewrite (e1 ? null : e22) as (e1 || e22)
                        e->Eoper = OPoror;
                        e->E2 = el_selecte2(e2);
                        goto beg;
                    }
                    if (!e22)
                    {
                        // Rewrite (e1 ? e22 : null) as (e1 && e21)
                        e->Eoper = OPandand;
                        e->E2 = el_selecte1(e2);
                        goto beg;
                    }
```