Update extensionController.php (#4571)

app/Controllers/extensionController.php

@@ -42,7 +42,7 @@ class FreshRSS_extension_Controller extends FreshRSS_ActionController {
 	 */
 	protected function getAvailableExtensionList() {
 		$extensionListUrl = 'https://raw.githubusercontent.com/FreshRSS/Extensions/master/extensions.json';
-		$json = file_get_contents($extensionListUrl);
+		$json = @file_get_contents($extensionListUrl);
 
 		// we ran into problems, simply ignore them
 		if ($json === false) {