Fix support .0 releases.

[0 is defined as empty](http://php.net/manual/en/function.empty.php#refsect1-function.empty-returnvalues) so releases like 7.x-1.0 would cause an exception to be thrown.
Minor can be non-numeric as it can be 2-rc3.

strlen > 0 is probably the best bet, as we want the empty string to count as "empty".