Fix ProgressQueue titles for cases, letters, etc.

Handles items with an alternate field that maps to title (like cases)
and items for which the title is usually filled in by updateDisplayTitle()
(like letters).

chrome/content/zotero/xpcom/progressQueue.js

@@ -154,7 +154,7 @@ Zotero.ProgressQueue = function (options) {
 		let row = {
 			id: item.id,
 			status: Zotero.ProgressQueue.ROW_QUEUED,
-			fileName: item.getField('title'),
+			fileName: item.getDisplayTitle(),
 			message: ''
 		};