[Kernel] Fix threading bug I think

src/core/kernel/threads.cpp

@@ -150,9 +150,9 @@ void Kernel::sleepThread(s64 ns) {
 	if (ns < 0) {
 		Helpers::panic("Sleeping a thread for a negative amount of ns");
 	} else if (ns == 0) { // Used when we want to force a thread switch
-		// TODO: Does sleep(0) always switch to another thread, or can it return to the same one if it's the highest prio one?
-		threads[currentThreadIndex].status = ThreadStatus::Ready;
-		switchToNextThread();
+		int curr = currentThreadIndex;
+		switchToNextThread(); // Mark thread as ready after switching, to avoid switching to the same thread
+		threads[curr].status = ThreadStatus::Ready;
 	} else { // If we're sleeping for > 0 ns
 		Thread& t = threads[currentThreadIndex];
 		t.status = ThreadStatus::WaitSleep;