You do acquire a Bonus Feat at level 9 and 17 from the Archetype's list, but lose Greater Tactician and Master Tactician. At level 18, it seems that you acquire nothing at all as your normal bonus feat selections at levels 6, 12, and 18, have been replaced.
Keep in mind by taking this archetype you lose "tactician, greater tactician, master tactician, and the standard cavalier's selection of bonus feats."
You, otherwise, gain the normal Cavalier abilities outside of the what the Archetype states.
Actually, unless I'm reading wrong you get bonus feats at 8 and 17. Gendarme says that the replacement bonus feats at 1st, then at 5th level and every 3 levels thereafter - so at 8, 11, 14, 17, and 20. Since the only thing you get at 9 is Master Tactician, that makes it a 'dead level' as well.
Or was it errata'd somewhere to be to at 1st, 5th, and then every 4 thereafter?
Regardless, yes - dead levels happen. Personally, I think they shouldn't but... ;)
"This ability replaces tactician, greater tactician, master tactician, and the standard cavalier's selection of bonus feats."
I do believe I added in intervals of 4 instead of 3 after level 5. Woops! Either way, the standard bonus feats you'd normally get, are gone.
As Xaratherus stated, levels 5, 8, 11, 14, 17, and 20 would be your bonus feats now, and only from the new ones listed with the Archetype.