Bugfix: Prevent crash when empty string set for INIT_INCREMENT or VALID_INCREMENT

Describe the Problem

Increment values are not needed if the [INIT/VALID]_BEG and [INIT/VALID]_END values are the same. If [INIT/VALID]_INCREMENT is not set in the METplus config, a default value of 60 seconds is used. However, if the increment value is set to an empty string, it causes a crash.

Expected Behavior

Setting the following should result in a successful run:

INIT_TIME_FMT = %Y%m%d%H
INIT_BEG = 2023111312
INIT_END = {INIT_BEG}
INIT_INCREMENT=

Environment

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To Reproduce

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Define Related Issue(s)

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[ ] METplus, MET, METdataio, METviewer, METexpress, METcalcpy, METplotpy

Bugfix Checklist

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dtcenter / METplus