Use the WebRequest::getCheck() shortcut where possible

Use the WebRequest::getCheck() shortcut where possible

This is inspired by Ib117e05.

As far as I can tell this is functionally identical. Even arrays should
behave the same, as both the getVal() and getCheck() methods do have a
special case that returns the `null` default in case the user tried to
pass multiple values instead of a single scalar.

Change-Id: Id4e4ec91f39d3c39461bd41673bdafc3bde11737