List index out of range when parsing a footprint with empty 'attr' field

[mvnmgrx]

When parsing this footprint, the empty attr token triggers a exception:

(footprint "Battery_CR1225"
  (layer "F.Cu")
  (tedit 5B93F51B)
  (descr "CR1225 battery")
  (tags "battery CR1225 coin cell")
  (attr)
  (fp_text reference "REF**" (at 0 -1) (layer "F.SilkS") hide
    (effects (font (size 1 1) (thickness 0.15)))
  )
  (fp_text value "Battery_CR1225" (at 0 0.5) (layer "F.Fab")
    (effects (font (size 1 1) (thickness 0.15)))
  )
  (fp_circle (center 0 0) (end 6.25 0) (layer "F.Fab") (width 0.1))
  (model "${KICAD6_3DMODEL_DIR}/Battery.3dshapes/Battery_CR1225.wrl"
    (offset (xyz 0 0 0))
    (scale (xyz 1 1 1))
    (rotate (xyz 0 0 0))
  )
)