Fix incorrect RC-handling for ZEND_EXT_STMT op1

Fixes GH-21504
Closes GH-21528

Author: iluuu1994

NEWS

@@ -7,6 +7,7 @@ PHP                                                                        NEWS
     destructors). (iliaal)
   . Fixed ZEND_API mismatch on zend_ce_closure forward decl for Windows+Clang.
     (henderkes)
+  . Fixed bug GH-21504 (Incorrect RC-handling for ZEND_EXT_STMT op1). (ilutov)
 
 - Iconv:
   . Fixed bug GH-17399 (iconv memory leak on bailout). (iliaal)

Zend/tests/gh21504.inc

@@ -0,0 +1,3 @@
+<?php
+
+'1234' |> var_dump(...);

Zend/tests/gh21504.phpt

@@ -0,0 +1,12 @@
+--TEST--
+GH-21504: Incorrect RC-handling for ZEND_EXT_STMT op1
+--FILE--
+<?php
+
+$php_escaped = getenv('TEST_PHP_EXECUTABLE_ESCAPED');
+$cmd = $php_escaped . ' -n -e ' . escapeshellarg(__DIR__ . '/gh21504.inc');
+echo shell_exec($cmd);
+
+?>
+--EXPECT--
+string(4) "1234"

Zend/zend_compile.c

@@ -1934,6 +1934,9 @@ static void zend_do_extended_stmt(znode* result) /* {{{ */
 
 	opline->opcode = ZEND_EXT_STMT;
 	if (result) {
+		if (result->op_type == IS_CONST) {
+			Z_TRY_ADDREF(result->u.constant);
+		}
 		SET_NODE(opline->op1, result);
 	}
 }