Kdenlive woes: libthumbnail going nuts

[Harald Albrecht]

This turns out to become even more strange with every turn: seems like 
I've managed to create some kind of killer project, albeit in a very 
literal sense when it comes to Kdenlive. I've noticed that loading the 
small project now takes very long, eats RAM like crazy ... which turns 
out to be eaten by libthumbnail.so.

I've now disabled thumbnails and created my small project anew from 
scratch. This time, it works in 17.12.0d without eating RAM like crazy 
so far.

I've also started fresh by moving kdenliveui.rc out of the way to be sure.

Nevertheless, this all feels very brittle... :(

Best regards,
Harald