Revert array_filter to fix a regression

config/sections/files.php

@@ -194,14 +194,14 @@
 				'multiple'   => $multiple,
 				'max'        => $max,
 				'api'        => $this->parent->apiUrl(true) . '/files',
-				'attributes' => [
+				'attributes' => array_filter([
 					// TODO: an edge issue that needs to be solved:
 					//		 if multiple users load the same section
 					//       at the same time and upload a file,
 					//       uploaded files have the same sort number
 					'sort'     => $this->sortable === true ? $this->total + 1 : null,
 					'template' => $template
-				]
+				])
 			];
 		}
 	],