Plugin and interface error

I installed MuseScore from the Debian Jessie's repo.

When I start MuseScore, it pops up several error dialog with following message:

Error loading plugin
"/usr/share/mscore-1.3/plugins/abc_import/abc_import.js"
line 56:
ReferenceError: Can't find variable: QDir

Error loading plugin
"/usr/share/mscore-1.3/plugins/musescore.com/musescore.com.js"
line 969:
ReferenceError: Can't find variable: QByteArray

Error loading plugin
"/usr/share/mscore-1.3/plugins/colornote.js" line 30:
ReferenceError: Can't find variable: QColor

After that, it runs, but labels on many toolbar buttons are missing: