bitbake: fix version comparison when one of the versions ends in .
Previously, this would happen:
======================================================================
ERROR: test_vercmpstring (bb.tests.utils.VerCmpString)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/alexander/development/poky/bitbake/lib/bb/tests/utils.py", line 45, in test_vercmpstring
result = bb.utils.vercmp_string('1.', '1.1')
File "/home/alexander/development/poky/bitbake/lib/bb/utils.py", line 143, in vercmp_string
return vercmp(ta, tb)
File "/home/alexander/development/poky/bitbake/lib/bb/utils.py", line 135, in vercmp
r = vercmp_part(va, vb)
File "/home/alexander/development/poky/bitbake/lib/bb/utils.py", line 124, in vercmp_part
elif ca < cb:
TypeError: '<' not supported between instances of 'NoneType' and 'int'
----------------------------------------------------------------------
Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>