Rethrow generator exception even without active stack frame

Finally blocks in generators may be invoked during shutdown, in
which case we don't have a stack frame. Similar to what
zend_call_function does, we still need to rethrow these exceptions,
otherwise they will be hidden (and leak).

Author: nikic

Zend/tests/generators/exception_during_shutdown.phpt

@@ -0,0 +1,30 @@
+--TEST--
+Generator exceptions during shutdown should not be swallowed
+--FILE--
+<?php
+
+function gen() {
+    try {
+        echo "before yield\n";
+        yield;
+        echo "after yield\n";
+    } finally {
+        echo "before yield in finally\n";
+        yield;
+        echo "after yield in finally\n";
+    }
+    echo "after finally\n";
+}
+
+$gen = gen();
+$gen->rewind();
+
+?>
+--EXPECTF--
+before yield
+before yield in finally
+
+Fatal error: Uncaught Error: Cannot yield from finally in a force-closed generator in %s:%d
+Stack trace:
+#0 {main}
+  thrown in %s on line %d

Zend/zend_generators.c

@@ -827,9 +827,10 @@ ZEND_API void zend_generator_resume(zend_generator *orig_generator) /* {{{ */
 		if (UNEXPECTED(EG(exception) != NULL)) {
 			if (generator == orig_generator) {
 				zend_generator_close(generator, 0);
-				if (EG(current_execute_data) &&
-				    EG(current_execute_data)->func &&
-				    ZEND_USER_CODE(EG(current_execute_data)->func->common.type)) {
+				if (!EG(current_execute_data)) {
+					zend_throw_exception_internal(NULL);
+				} else if (EG(current_execute_data)->func &&
+						ZEND_USER_CODE(EG(current_execute_data)->func->common.type)) {
 					zend_rethrow_exception(EG(current_execute_data));
 				}
 			} else {