Hopefully fix crash in ContextView on startup

It is strange that simple initialization to zero fixes the problem, but
it fixes the crash for at least one reporter.

Reporters, please rebuild Amarok from current git and should loudly if
you can still reproduce the bug.

BUGFIXES:
 * Fix crash on startup related to ContextView

BUG: 258741
FIXED-IN: 2.6
DIGEST: Amarok crashfix