[ContextManager] Check if there is a current context before "freeing" it

emper/ContextManager.cpp

@@ -51,8 +51,11 @@ void ContextManager::start() {
 	// We perform a longjmp with fibrilResumeValue == 0 to switch back
 	// to the original stack and terminate the runtime.
 	if (unlikely(!fibrilResumeValue && runtime.isTerminating())) {
-		putFreeContext(Context::currentContext);
-		Context::currentContext = nullptr;
+		Context* currentContext = Context::currentContext;
+		if (currentContext) [[likely]] {
+			Context::currentContext = nullptr;
+			putFreeContext(currentContext);
+		}
 		return;
 	}