Bugfix for calculating PCT values

[TatianaBurek]

Describe the Problem

It is possible that sum_n_i_orig_T value is 0 when there is no data available for the parameters. In this case agg_stat.py is failing and exiting without further calculations:
agg_stat.py line 1092

# calculate o_bar
o_bar = oy_total / sum_n_i_orig_T

need to anticipate and handle this situation
Suggestion:

 # calculate o_bar
 if sum_n_i_orig_T != 0:
                            o_bar = oy_total / sum_n_i_orig_T
 else:
                            o_bar = None

scorecard_rrfs_REFC_prob.agg_stat.info.txt
scorecard_rrfs_REFC_prob.data.agg_stat.txt

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