Hotfix: TrackFit parameters: Fix backward compatibility with < 5.9.0.

For ACQt < 5.9.0 we need to work with the fParametersOld variable
instead of fParameters which was introduced in 5.9.0.
Hotfix: TOFBeta::BetaError() Restore compatibility with < 5.9.0.

In ACQt < 5.9.0 fBetaError is stored directly and cannot be accessed via
fInverseBetaError as that variable is 0 for old files.
Provide accessor for ClusterDistance vector for <= 5.8.0.

This is just to provide some way to access the information stored in the
old ACQt files. Currently neither this function nor the 5.9.0 version
are used anywhere in dev.
Safety check in FileManager::ResetACQtFiles().

This prevents a crash when the FileManager is not properly initialized
and ResetACQtFiles() is called nevertheless.