To reproduce:
=============
install conditional step plugin ver 0.0.2
create a new matrix project
open project configuration page
click "Add Build Step"
Selections "conditional step" (single) and (mupltiple) are missing in the dropdown list

Notes:
======

• plugin works for simple free-style projects
• previous version 0.0.1 works for matrix projects
• some other plugins (for example "copy artifact") are also suppressed after "conditional-buildstep" ver 0.0.2 is installed