fix potential crash in multi-threading

common/dangle/DangleContext.h

@@ -69,6 +69,7 @@ namespace dangle {
             using Op = std::function<void(void)>;
 
             bool destroy = false;
+            std::mutex destroyMutex;
 
             // Ops are combined into batches:
             //   1. A batch is always executed entirely in one go on the GL thread
@@ -97,6 +98,8 @@ namespace dangle {
             // [JS thread] Add a blocking operation to the 'next' batch -- waits for the
             // queued function to run before returning
             void addBlockingToNextBatch(Op &&op) noexcept {
+                std::unique_lock<std::mutex> lock(destroyMutex);
+
                 if (destroy) {
                     DangleSysLog("addBlockingToNextBatch after DangleContext destroyed");
                     return;
@@ -260,6 +263,11 @@ namespace dangle {
                 });
             }
 
+            ~DangleContext() {
+                std::unique_lock<std::mutex> lock(destroyMutex);
+                DangleSysLog("~DangleContext()");
+            }
+
             static DangleContext *ContextGet(UDangleContextId dangleCtxId);
 
             static UDangleContextId ContextCreate(jsi::Runtime &runtime);