Fix startup errors due to missed schema update steps for retractedItems

I don't know how this is happening -- people are ending up with an
updated DB version but missing schema changes, despite the DB version
being updated after the schema updates and in the same transaction --
but until we figure it out, apply the schema update steps in
Zotero.Retractions.init() if necessary.

chrome/content/zotero/xpcom/retractions.js

@@ -48,6 +48,14 @@ Zotero.Retractions = {
 			return;
 		}
 		
+		// TEMP: Until we can figure out why some schema updates aren't going through despite the
+		// version number being incremented, create table here if it's missing
+		await Zotero.DB.queryAsync("CREATE TABLE IF NOT EXISTS retractedItems (\n	itemID INTEGER PRIMARY KEY,\n	data TEXT,\n	FOREIGN KEY (itemID) REFERENCES items(itemID) ON DELETE CASCADE\n);");
+		try {
+			await Zotero.DB.queryAsync("ALTER TABLE retractedItems ADD COLUMN flag INT DEFAULT 0");
+		}
+		catch (e) {}
+		
 		// Load mappings of keys (DOI hashes and PMIDs) to items and vice versa and register for
 		// item changes so they can be kept up to date in notify().
 		await this._cacheKeyMappings();

chrome/content/zotero/xpcom/schema.js

@@ -2513,6 +2513,7 @@ Zotero.Schema = new function(){
 				}
 			}
 			
+			// Duplicated in retractions.js::init() due to undiagnosed schema update bug
 			else if (i == 105) {
 				// This was originally in 103 and then 104, but some schema update steps are being
 				// missed for some people, so run again with IF NOT EXISTS until we figure out