scripting: Add null window guard in WorkspaceWrapper::clientArea()
Workspace::clientArea(clientAreaOpt, Window*) expects a valid pointer. BUG: 458598 (cherry picked from commit 287ad956)
Workspace::clientArea(clientAreaOpt, Window*) expects a valid pointer. BUG: 458598 (cherry picked from commit 287ad956)
mentioned in commit 1a7fe73c