2 problems using NullVoice to align lyrics

[Luming]

1. When I added a NullVoice into a staff with a existing homophony Voice, 
all previously-correctly-placed rest marks are engraved in a polyphonic
manner (in the lower-half of the staff instead of in the middle), unless it
is a "r" or a "s" in the NullVoice at the same time.
I did not notice any mark besides rest mark having this problem. All notes
are engraved correctly.
Using "\oneVoice" command on the rest marks did not fix this.

2. When using " word __ " to create a extender line in Lyrics, if the note
that the word aligned to is from a NullVoice and followed by "r" or "s", the
extender line will extend all the way until first note after the followed
rests, instead of stopping after last tied/slurred note.

Thank you for reading this.
I'm new to LilyPond and I work with Windows 8.1, Frescobaldi 2.0.16 and
Lilypond 2.18.2