[core] Use weak scheduler inside mailbox

There is no guarantee that scheduler is alive when message
is pushed to the mailbox.

1 files changed, 3 insertions, 1 deletions

diff --git a/include/mbgl/actor/mailbox.hpp b/include/mbgl/actor/mailbox.hpp
index 2b9838ef29..1e18d593d3 100644
--- a/include/mbgl/actor/mailbox.hpp
+++ b/include/mbgl/actor/mailbox.hpp
@@ -7,6 +7,8 @@
 #include <mutex>
 #include <queue>
 
+#include <mapbox/weak.hpp>
+
 namespace mbgl {
 
 class Scheduler;
@@ -38,7 +40,7 @@ public:
     static std::function<void()> makeClosure(std::weak_ptr<Mailbox>);
 
 private:
-    optional<Scheduler*> scheduler;
+    mapbox::base::WeakPtr<Scheduler> weakScheduler;
 
     std::recursive_mutex receivingMutex;
     std::mutex pushingMutex;