Handle case when CPBox is used as a separator line having no title

If _titlePosition is correctly set to CPNoTitle value, class already handles removing title view from display.
Previously, _titlePosition was not correctly set, title view was left in place.
With no supplied value for title, outline of title view was rendered with visible artifacts.

AppKit/CPBox.j

@@ -630,7 +630,11 @@ var CPBoxTypeKey          = @"CPBoxTypeKey",
             [_contentView setSubviews:[malformedContentView subviews]];
             [self replaceSubview:malformedContentView with:_contentView];
         }
-
+        else
+        {
+            _titlePosition = CPNoTitle;        
+        }
+        
         [self setAutoresizesSubviews:YES];
         [_contentView setAutoresizingMask:CPViewWidthSizable | CPViewHeightSizable];