The "Value" slider handle in the slider component disappears when Min value is greater than Max value.

Steps to Reproduce:
1. Create a new project.
2. Create a Canvas and add a Slider to it.
3. Increase Min value in its slider component.
4. Make sure that Min value is greater than Max value.

Observed Result : Slider handle for Value disappears.

Expected Result: Slider handle for value shouldn't disappear for any value.

Reproducible On: 2018.3.0a9, 2018.3.0a1

Not Reproducible On: 2018.2.0f2

Environment: Occurs On Windows and Mac