restore Maverics support

In commit 8e8961ac8a65c2dc8812d6c2ddafc2d56b4831ce, the assertion on
the number of version components was simply changed to support
Yosemite, but the older value of 3 from Maverics would no longer pass
the assertion.  The rest of the code was fine, so we just need to
change the assert.