(let*
((paper-height (ly:output-def-lookup layout 'paper-height))
(paper-width (ly:output-def-lookup layout 'paper-width))
-
- (lmargin (ly:output-def-lookup layout 'left-margin))
+ (lmargin (ly:output-def-lookup layout 'left-margin #f))
(left-margin (if lmargin
lmargin
(/ (- paper-width