Mea culpa. The `DCHECK` needs to be an `if`.

Change-Id: Ifaf7e0c4d51cf40c404b1e40c595d93afa814139
Reviewed-on: https://code-review.googlesource.com/c/re2/+/60090
Reviewed-by: Randall Bosetti <rlb@google.com>
Reviewed-by: Paul Wankadia <junyer@google.com>
diff --git a/re2/prefilter_tree.cc b/re2/prefilter_tree.cc
index 8e07134..409794e 100644
--- a/re2/prefilter_tree.cc
+++ b/re2/prefilter_tree.cc
@@ -271,9 +271,10 @@
         log_num_triggered -= log_num_regexps;
       } else if (parents.size() > 9) {
         auto it = std::find(parents.begin(), parents.end(), id);
-        DCHECK(it != parents.end());
-        parents.erase(it);
-        entries_[id].propagate_up_at_count--;
+        if (it != parents.end()) {
+          parents.erase(it);
+          entries_[id].propagate_up_at_count--;
+        }
       }
     }
   }