PreviewClient: fix problem when line number = 0
PreviewClient: fix problem when line number = 0

araisrobo/QtQuickVcp,strahlex/QtQuickVcp,araisrobo/QtQuickVcp,qtquickvcp/QtQuickVcp,machinekoder/QtQuickVcp,araisrobo/QtQuickVcp,machinekoder/QtQuickVcp,machinekoder/QtQuickVcp,strahlex/QtQuickVcp,qtquickvcp/QtQuickVcp,qtquickvcp/QtQuickVcp,araisrobo/QtQuickVcp,machinekoder/QtQuickVcp,qtquickvcp/QtQuickVcp,JDSquared/QtQuickVcp,JDSquared/QtQuickVcp,strahlex/QtQuickVcp,JDSquared/QtQuickVcp,JDSquared/QtQuickVcp