Fix exception handling in shm_put_var() (#19279)

ext/sysvshm/sysvshm.c

@@ -261,7 +261,9 @@ PHP_FUNCTION(shm_put_var)
 		RETURN_THROWS();
 	}
 
-	ZEND_ASSERT(shm_var.s != NULL);
+	if (UNEXPECTED(shm_var.s == NULL)) {
+		RETURN_THROWS();
+	}
 
 	/* insert serialized variable into shared memory */
 	bool ret = php_put_shm_data(shm_list_ptr->ptr, shm_key, shm_var.s);

ext/sysvshm/tests/serialize_exception.phpt

@@ -0,0 +1,27 @@
+--TEST--
+__serialize() exception in shm_put_var()
+--EXTENSIONS--
+sysvshm
+--FILE--
+<?php
+
+$key = ftok(__FILE__, 't');
+$s = shm_attach($key, 1024);
+
+class Test {
+    public function __serialize() {
+        throw new Error("no");
+    }
+}
+
+try {
+    shm_put_var($s, 1, new Test);
+} catch (Error $exception) {
+    echo $exception->getMessage() . "\n";
+}
+
+shm_remove($s);
+
+?>
+--EXPECT--
+no