Skim operation fails due to file access errors on EOS when reusing output directory

When running examples/nanozmumu.py with an existing output directory, the skim operation (muSkim) fails with ROOT file access errors, leading to a crash. Deleting the output directory resolves the issue.Steps to Reproduce the issue:

1. Run the analysis once (works fine):

   bambooRun -m examples/nanozmumu.py:NanoZMuMu examples/test1.yml -o test5 --maxFiles=1

2. Re-run without deleting test5:

   Error in <TFile::cd>: No such file root://eoshome-k.cern.ch//eos/user/k/kjaffel/bamboodev/bamboo/test5/results/DY_M50_test.root:/
   TTree::CopyEntries:0: RuntimeWarning: The output TTree (muSkim) must be associated with a writable file (/tmp/kjaffel/tmp8gtvv90_/skim_muSkim.root).
   Error in <TTree::CloneTTree>: TTree has not been cloned

3. Solution: Manually delete test5 before re-running.

Bamboo should either log warnings if the output directory exists or overwrite existing files cleanly when detect EOS/XRootD connectivity.