Be less restrictive with handling of Enter or Return keys in Articles…

… tab

Fix issue #454

src/AppController.m

@@ -2744,7 +2744,7 @@ -(BOOL)handleKeyDown:(unichar)keyChar withFlags:(NSUInteger)flags
 					[self viewSourceHomePage:self];
 				return YES;
 			}
-			else if ([mainWindow firstResponder] == [mainArticleView mainView])
+			else
 			{
 				if (flags & NSAlternateKeyMask)
 					[self viewArticlePagesInAlternateBrowser:self];