Fix overwriting bug in of file parameter

For some reason a previous attempt at making this pull decided the entire file was new (and I had made a typo in it)

Fixes bug
http://www.concrete5.org/developers/bugs/5-6-1-2/loaderpackageelement-breaks-on-file-as-parameter/

Note that $env and $args parameters may also be susceptible to similar bugs.

For some reason the git editor has done it again. I give up. The only lines I changed are between lines 80 and 101. The rest is erroneous comparison introduced by git.