Handle invalid titles

Picksome had logic which would result in an error if the list of titles
included any invalid characters (or otherwise violated the list of rules
for wiki page titles as described in
https://en.wikipedia.org/wiki/Wikipedia:Page_name#Technical_restrictions_and_limitations)

By separating the title generation we are able to check for a null
result (null is returned in the event of an invalid title) and skip that
result instead of triggering the error.

Issue #135

roles/picksome/files/picksome.php

@@ -30,7 +30,8 @@ $wgPickSomePage = function($title) {
     $valid_pages = [];
     preg_match_all("/\\[\\[([^\\]]*)\\]\\]/", $page->getContent()->getText(), $valid_pages);
     foreach($valid_pages[1] as $valid_page) {
-      if($title->equals(Title::newFromText($valid_page))) {
+      $valid_page_title = Title::newFromText($valid_page);
+      if($valid_page_title && $title->equals($valid_page_title)) {
         return true;
       }
     }