Empty pandas Series should have dtype

[nikosavola]

Currently, I get

FutureWarning: The default dtype for empty Series will be 'object' instead of 'float64' in a future version. Specify a dtype explicitly to silence this warning.
Ljs = pd.Series({})

many times from core_distributed_analysis.py when running simply do_EPR_analysis().

The fix is to explicitly write the correct dtype to all the Series in the code

[zlatko-minev]

Ah yeah that's a good one to fix.