Fix compilation for PHP 8.1

Accidentally introduced in 175ff60. arData was
not part of an anonymous union.

Author: iluuu1994

Zend/zend_hash.c

@@ -240,7 +240,7 @@ ZEND_API const HashTable zend_empty_array = {
 	.gc.u.type_info = IS_ARRAY | (GC_IMMUTABLE << GC_FLAGS_SHIFT),
 	.u.flags = HASH_FLAG_UNINITIALIZED,
 	.nTableMask = HT_MIN_MASK,
-	{.arData = (Bucket*)&uninitialized_bucket[2]},
+	.arData = (Bucket*)&uninitialized_bucket[2],
 	.nNumUsed = 0,
 	.nNumOfElements = 0,
 	.nTableSize = HT_MIN_SIZE,