Fixed PageStorage detecting files as pages

CHANGELOG.md

@@ -4,6 +4,7 @@
 1. [](#bugfix)
     * Ignore errors when using `set_time_limit` in `Archiver` and `GPM\Response` classes [#3023](https://github.com/getgrav/grav/issues/3023)
     * Fixed moving page to itself causing the page folder to be lost (converted to an empty file)
+    * Fixed `PageStorage` detecting files as pages
 
 # v1.7.9
 ## 03/19/2021

system/src/Grav/Common/Flex/Types/Pages/Storage/PageStorage.php

@@ -534,7 +534,7 @@ class PageStorage extends FolderStorage
             $markdown = [];
             $children = [];
 
-            if (is_string($path) && file_exists($path)) {
+            if (is_string($path) && is_dir($path)) {
                 $modified = filemtime($path);
                 $iterator = new FilesystemIterator($path, $this->flags);