Remove monsters from the transit list when dactions kill them.

This could happen with when DACT_END_SPIRIT_HOWL resets the remaining
spirit wolves that are not in LOS.  See for example !lg Apol crash 1

There still may be other situations that put or leave dead monsters in
the transit list: see #7146.

1 files changed, 6 insertions, 0 deletions

diff --git a/crawl-ref/source/mon-transit.cc b/crawl-ref/source/mon-transit.cc
index d32b1ffab3..0555bedc70 100644
--- a/crawl-ref/source/mon-transit.cc
+++ b/crawl-ref/source/mon-transit.cc
@@ -256,6 +256,12 @@ void apply_daction_to_transit(daction_type act)
             monster* mon = &j->mons;
             if (mons_matches_daction(mon, act))
                 apply_daction_to_mons(mon, act, false, true);
+
+            // If that killed the monster, remove it from transit.
+            // Removing this monster invalidates the iterator that
+            // points to it, so decrement the iterator first.
+            if (!mon->alive())
+                m->erase(j--);
         }
     }
 }