fix: add: threads to process

src/multitasking/thread.c

@@ -28,9 +28,14 @@ struct tcb *create_thread(struct pcb *process, void (*routine)(void))
 	new_tcb->state = NEW;
 
 	struct tcb *it = process->thread_list;
-	while (it)
-		it = it->next;
-	it = new_tcb;
+	if (it) {
+		while (it)
+			it = it->next;
+		it = new_tcb;
+	}
+	else {
+		process->thread_list = new_tcb;
+	}
 
 	return new_tcb;
 }