Unwanted horizontal space below lyrics of first system only -- example file

[Mirosław]

% With polyfonic lyrics there is unwanted space below lyrics of first system 
(only) when second voice starts later (specially after first system).

\version "2.6.4"
\include "deutsch.ly"

refren = \set stanza = "R."
zwrotka = \set stanza = "1."
alteracja = #(set-accidental-style 'modern)

klucz = \key c \major
takt = \time 4/4

melodiaI = { c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c 
d 
e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f \voiceOne c d e f c 
d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c 
d e f c d e f c d e f c d e f c d e f \bar "|." }

melodiaII = { \skip 1*16 c d e f c d e f c d e f c d e f c d e f c d e f c d e 
f 
c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f }

tekstI = \lyricmode { \zwrotka c d e f c d e f c d e f c d e f c d e f c d e f 
c 
d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c 
d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c 
d e f c d e f c d e f c d e f c d e f c d e f }

tekstII = \lyricmode { \zwrotka c d e f c d e f c d e f c d e f c d e f c d e f 
c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f c d e f
 }

\paper {
        #(set-paper-size "a6")
        #(layout-set-staff-size (* 14.0 pt))
        leftmargin = 7 \mm
        linewidth = 88 \mm
        indent = 0 \mm
        betweensystemspace = #0.1 %#(* 1.0 mm)
        betweensystempadding = #0.1 %#(* 1.0 mm)
}
\layout {
        \context { \Score \remove "Bar_number_engraver" }
        \context { \Staff minimumVerticalExtent = ##f autoBeaming = ##f }
        \context { \Lyrics minimumVerticalExtent = #'(0.0 . 2.2) }
}

\score {
        \new Staff %\transpose c c
        {
                \klucz
                \takt
                \alteracja
                \relative c' { <<
                        \context Voice = "1" { \melodiaI }
                        \new Lyrics \lyricsto "1" \tekstI
                        \context Voice = "2" { \voiceTwo \melodiaII }
                        \new Lyrics \lyricsto "2" \tekstII
                >> }
        }
}