Make sure Title is not NULL

extension.json

 {
   "name": "WSSlots",
-  "version": "1.4.1",
+  "version": "1.4.2",
   "namemsg": "wsslots-extensionname",
   "url": "https://wikibase-solutions.com",
   "type": "other",
@@ -70,4 +70,4 @@
     "editslot": "WSSlots\\ApiEditSlot"
   },
   "manifest_version": 2
-}
\ No newline at end of file
+}

src/ParserFirstCallInitHookHandler.php

@@ -111,7 +111,7 @@ class ParserFirstCallInitHookHandler implements ParserFirstCallInitHook {
 
 		$title = \Title::newFromText( $page_name );
 
-		if ( !$title->exists() ) {
+		if ( $title === null || !$title->exists() ) {
 			return false;
 		}