Shorten stem are not read correctly

Steps to reproduce bug
1. place a note and shorten its stem than default.
2. save
3. re-open

Expected behavior
short stem should have been short as saved.

Actual behavior
short stem became long than saved.

Version number
2.0 release and self built (revision 772c691dcbb8f162257cbdc764f079da6c4f19fe)

Operating system
Windows7 SP1 64bit

Details
a note whose stem length is longer or shorter than default has Stem::_userLen property.
shorter one has minus value of Stem::_userLen.
saved value of Stem::_userLen is valid,
but loaded and re-saved value of Stem::_userLen is flipped to plus value.