SystemUI: Use appropriate function when trying to retrieve colorError

* android.R.attr.colorError is not a color state list,
  therefore we cannot use getDefaultColor(ctx, resid)
  on it.
* Fixes : https://gitlab.com/LineageOS/issues/android/issues/1010

Change-Id: If39b0c066c904884283a9dc62ec85bf6450c1dda