Open Radar

 
Summary:
I created a UILabel in an IB storyboard, selected "Attributed text", and clicked the "…" button to edit the text attributes. Although [the documentation](https://developer.apple.com/library/ios/documentation/Cocoa/Reference/ApplicationKit/Classes/NSParagraphStyle_Class/index.html#//apple_ref/occ/instp/NSParagraphStyle/tailIndent) says that the value can be negative, IB will not let the value be set less than 0.

Steps to Reproduce:
1. Drag a UILabel onto a view in a storyboard.
2. In its Attributes Inspector, select "Attributed" from the "Text" drop down menu.
3. Click the "…" button and enter "-5" in the "Tail" field

Expected Results:
I expected the -5 to stick.

Actual Results:
The value resets to 0.

Version:
Version 6.0.1 (6A317)

Notes:
I was able to work around this issue by editing the storyboard file directly. Now the -5 appears in the "Tail" field, but I'm afraid of what will happen if I ever inadvertently edit it.