Return empty string from SplFileInfo::getPathname()

Instead of false. This is consistent with how other methods like
SplFileInfo::getPath() behave. It's also a requirement before
SplFileInfo::__toString() calls SplFileInfo::getPathname() and
needs to return a string.

ext/spl/spl_directory.c

@@ -1045,7 +1045,7 @@ PHP_METHOD(SplFileInfo, getPathname)
 	if (path != NULL) {
 		RETURN_STRINGL(path, path_len);
 	} else {
-		RETURN_FALSE;
+		RETURN_EMPTY_STRING();
 	}
 }
 /* }}} */

ext/spl/spl_directory.stub.php

@@ -18,7 +18,7 @@ class SplFileInfo
     /** @return string */
     public function getBasename(string $suffix = "") {}
 
-    /** @return string|false */
+    /** @return string */
     public function getPathname() {}
 
     /** @return int|false */

ext/spl/spl_directory_arginfo.h

@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 55701f921c7df2f344dd6b110558fd97efec9891 */
+ * Stub hash: 444071056e55fdc44d76db009c92b4d06eba81fb */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_SplFileInfo___construct, 0, 0, 1)
 	ZEND_ARG_TYPE_INFO(0, file_name, IS_STRING, 0)