[runtime stats] Fix crash when RCS are enabled dynamically.

src/counters.cc

Index: src/counters.cc
diff --git a/src/counters.cc b/src/counters.cc
index d8061f5f3341a2917480713596c6c536f1e8d77e..6e7c1cb90c740ca7ebc5ef45c63a5db267ecbabc 100644
--- a/src/counters.cc
+++ b/src/counters.cc
@@ -309,9 +309,10 @@ void RuntimeCallStats::Leave(RuntimeCallStats* stats, RuntimeCallTimer* timer) {
 // static
 void RuntimeCallStats::CorrectCurrentCounterId(RuntimeCallStats* stats,
                                                CounterId counter_id) {
-  DCHECK_NOT_NULL(stats->current_timer_.Value());
-  RuntimeCallCounter* counter = &(stats->*counter_id);
-  stats->current_timer_.Value()->counter_ = counter;
+  RuntimeCallTimer* timer = stats->current_timer_.Value();
+  // When RCS are enabled dynamically there might be no current timer set up.
+  if (timer == nullptr) return;
+  timer->counter_ = &(stats->*counter_id);
 }
 
 void RuntimeCallStats::Print(std::ostream& os) {