Zero initialize all pointer class and struct members

This prevents the pitfall of UB when checking if they have been
assigned something valid by comparing to nullptr.

core/templates/command_queue_mt.h

@@ -311,7 +311,7 @@ class CommandQueueMT {
 	};
 
 	struct SyncCommand : public CommandBase {
-		SyncSemaphore *sync_sem;
+		SyncSemaphore *sync_sem = nullptr;
 
 		virtual void post() {
 			sync_sem->sem.post();