pretty-print and localAlterations

[Simon Albrecht]

Hello,

if I compile the following code:

%%%%%%%%
\version "2.19.32"
#(use-modules (ice-9 pretty-print))

printKeysig =
\applyContext #(lambda (context)
                 (format #t "~a" (pretty-print (ly:context-property context
'localAlterations))))
\relative {
  es'4 \printKeysig e'
}
%%%%%%%%

I get a spurious #<unspecified> in the console output, on its own line.
Of course, it’s not an actual problem, but I’d still be curious where it 
comes from.

Yours, Simon