Bugfix: Fix the TC-Stat RIRW runtime error when computing CTS statistics from an empty contingency table

[JohnHalleyGotway]

Describe the Problem

This issue was identified based on feedback from the NOAA METplus Telecon on 5/15/2023 from Olivia Ostwald. TC-Stat produces a runtime error when attempting to compute CTS statistics from an empty contingency table. A short-term solution of only requesting CTC output with -out_line_type CTC will work for the time being. Recommend fixing this in the develop branch for MET version 11.1.0 but not providing a patch in the main_v11.0 branch.

Expected Behavior

Computing CTS stats for an empty contingency table produces a runtime error from ContingencyTable::gheidke_ec(double). Recommend removing the empty table check and just return bad data instead. The error goes away if you only request -out_line_type CTC output, and the contingency table counts for that empty table are indeed written:

COL_NAME: ATIME  BTIME  AEXACT BEXACT ATHRESH BTHRESH WINDOW_BEG WINDOW_END AMODEL TOTAL FY_OY FY_ON FN_OY FN_ON EC_VALUE
RIRW_CTC: 240000 240000 true   true   >=30.0  >=30.0  000000     000000     BCLP       0     0     0     0     0      0.5

Testing this same situation using MET version 10.1.0, prior to the addition of the HSS_EC column, an empty contingency table from the RIRW job just produced a CTC line with all stats computed as NA. Recommend fixing the code to do the same... do not error out because of an empty table.

Environment

Can be reproduced on seneca.

To Reproduce

Run the following on seneca:

cd /d1/projects/MET/MET_regression/develop/NB20230515/MET-develop/test_output
# This runs fine
 ../bin/tc_stat -lookin tc_pairs/alal2010.tcst -job rirw -out_line_type CTC,CTS
# Adding -by amodel errors out
 ../bin/tc_stat -lookin tc_pairs/alal2010.tcst -job rirw -out_line_type CTC,CTS -by amodel
ERROR  : 
ERROR  : ContingencyTable::gheidke_ec(double) -> table empty!
ERROR  : 

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[JohnHalleyGotway]

Note that for the HSS statistic in the CTS line type, MET calls TTContingencyTable::hss() which does NOT check for an empty contingency table. An empty table results in bad data to avoid dividing by 0.

For the HSS_EC statistic in the CTS line type, MET calls ContingencyTable::gheidke_ec(double ec_value) which does current error out for empty contingency tables. The same function is used for both the CTS and MCTS output line types.

So that explains why this issue didn't show up for the HSS statistic but does show up for HSS_EC.