[SailfishDevel] Prototype 'TextBaseItem' from 'TextBase' could not be resolved (M301)

[info at flyingfischer.ch]

Just in case any body else runs into the error

(process:957): dconf-CRITICAL **: unable to open file 
'/etc/dconf/db/vendor': /etc/dconf/db/vendor: invalid gvdb header; 
expect degraded performance

I got this error only with the VirtualBox OSE (Open Source Edition) on 
Ubuntu. That's how I resloved it:

Deinstalled Sailfish IDE

sudo apt-get purge virtualbox virtualbox-qt virtualbox-dkms 
virtualbox-guest-dkms

Install Virtualbox from here

https://www.virtualbox.org/wiki/Linux_Downloads

Reinstall Sailfish IDE

Markus