Skip set the volume when slider is not initialized

Setting value on slider without initialized the correct range will cause
crashes. Make sure the min/max value is set before setting the value on
slider.

Flag: EXEMPT bugfix
Bug: 421036851
Test: manually test with real device
Test: atest AmbientVolumeUiControllerTest
Test: atest AmbientVolumeControllerTest
Change-Id: Idd901361123544c5ec88c5ba18ab53fdb9aa68b3