TQAnalysisAlgorithm initializing cuts when no tree is available

As we cannot connect any input branches we may not initialize cuts (and thereby Observables) if no actual tree is present (this regularly happens in case no event makes it past the preselection in PAODs for example, we still need to account for the file's meta data such as sumOfWeights though).

In the MCASV we already have dedicated checks because of this, the TQAnalysisAlgorithm, however, does not account for this yet.

This has lead to a MR (!652 (closed)) which addresses this problem by making cuts less strict and relying on such an error being handled upstream.

A better more narrow fix may be a bit safer (i.e. replicating the explicit check for a tree and entries>0 in the AnalysisAlgorithm) as this would still cause TQCut to throw an error if used inproperly via some other code path.