posix: pthread_getspecific: fix for coverity issue cid 334909

* remove unneeded line of code that duplicated the first part
  of the SYS_SLIST_FOR_EACH_NODE() expansion.
* return NULL if pthread_self() is not a valid pthread

Signed-off-by: Christopher Friedt <[email protected]>

Author: Christopher Friedt

lib/posix/key.c

@@ -248,12 +248,17 @@ int pthread_setspecific(pthread_key_t key, const void *value)
 void *pthread_getspecific(pthread_key_t key)
 {
 	pthread_key_obj *key_obj;
-	struct posix_thread *thread = to_posix_thread(pthread_self());
+	struct posix_thread *thread;
 	pthread_thread_data *thread_spec_data;
 	void *value = NULL;
 	sys_snode_t *node_l;
 	k_spinlock_key_t key_key;
 
+	thread = to_posix_thread(pthread_self());
+	if (thread == NULL) {
+		return NULL;
+	}
+
 	key_key = k_spin_lock(&pthread_key_lock);
 
 	key_obj = get_posix_key(key);
@@ -262,8 +267,6 @@ void *pthread_getspecific(pthread_key_t key)
 		return NULL;
 	}
 
-	node_l = sys_slist_peek_head(&(thread->key_list));
-
 	/* Traverse the list of keys set by the thread, looking for key */
 
 	SYS_SLIST_FOR_EACH_NODE(&(thread->key_list), node_l) {