Fix handling of exception if valid() during yield from

Fixes oss-fuzz #25296.

Zend/tests/generators/yield_from_valid_exception.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Exception from valid() during yield from
+--FILE--
+<?php
+
+class FooBar implements Iterator {
+    function rewind() {}
+    function current() {}
+    function key() {}
+    function next() {}
+    function valid() {
+        throw new Exception("Exception from valid()");
+    }
+}
+
+function gen() {
+    try {
+        yield from new FooBar;
+    } catch (Exception $e) {
+        echo $e->getMessage(), "\n";
+    }
+}
+
+$x = gen();
+$x->current();
+
+?>
+--EXPECT--
+Exception from valid()

Zend/zend_generators.c

@@ -709,6 +709,9 @@ static int zend_generator_get_next_delegated_value(zend_generator *generator) /*
 		}
 
 		if (iter->funcs->valid(iter) == FAILURE) {
+			if (UNEXPECTED(EG(exception) != NULL)) {
+				goto exception;
+			}
 			/* reached end of iteration */
 			goto failure;
 		}