Fixed incorrect refcountion inference for BW_NOT

BW_NOT for emtpy string returns empty string

Fixes oss-fuzz #41280

Author: dstogov

ext/opcache/Optimizer/zend_inference.c

@@ -2402,7 +2402,7 @@ static zend_always_inline int _zend_update_type_info(
 		case ZEND_BW_NOT:
 			tmp = 0;
 			if (t1 & MAY_BE_STRING) {
-				tmp |= MAY_BE_STRING | MAY_BE_RC1;
+				tmp |= MAY_BE_STRING | MAY_BE_RC1 | MAY_BE_RCN;
 			}
 			if (t1 & (MAY_BE_ANY-MAY_BE_STRING)) {
 				tmp |= MAY_BE_LONG;

ext/opcache/tests/jit/bw_not_001.phpt

@@ -0,0 +1,20 @@
+--TEST--
+JIT BW_NOT: 001 Incorrect refcounting inference
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit_buffer_size=1M
+opcache.protect_memory=1
+--FILE--
+<?php
+$x[~"$x"]*=1;
+?>
+DONE
+--EXPECTF--
+Warning: Undefined variable $x in %sbw_not_001.php on line 2
+
+Warning: Undefined variable $x in %sbw_not_001.php on line 2
+
+Warning: Undefined array key "" in %sbw_not_001.php on line 2
+DONE