logic pro 9 extreme fail

Hi.

I bought logic pro 9 painfully near the release of logic pro x. Obviously if I'd known x was coming out I wouldn't have done so, but never mind.
Regardless, I'm having issues with 9 at the moment - when the playhead moves it leaves a trail of blackness everywhere. I have no idea why, but when I looked elsewhere on here, the suggestion was to upgrade to 9.1.8. I checked and realised I was still on 9.1.6, so I downloaded the upgrade from apple and tried to install it.

I was met with the following message...
"The version of Logic Pro installed on this Mac must be updated through the Mac App Store. Check the Mac App Store to see if an update is available."

Of course, this is impossible now, since the app store only has logic pro x.

Is there any way to get around this or are apple just forcing me to pay yet another £140 if I want to keep using their software?
I like apple products, but they really seem to screw you over when it comes to upgrades/updating.