Proportional layer size changes can result in layers of invalid size

[iwehrman]

As reported by @ktaki in #3717:

When W and H values are linked, it is still possible to make [layer width or height] <1 [which results in broken document state]. Try with a text box layer W=200 and H=600. Link the value, then set H=1. This will result in the W to be less than 1 and reproduce the original issue. In fact, this can be an issue with vector layers also. It is possible to set to the value smaller than 0.1.

[iwehrman]

A core bug that asks Photoshop to clamp the width/height to a valid range: https://jira.corp.adobe.com/browse/PS-1384