[3pt] synthesize_test_cases.py annoying error (very large number of them)

[RobHanna-NOAA]

Soon we will merge PR 1217 with updates for OpenJDK and a bunch of python packages. One of the upgrades is for numpy.

This has triggered a new warning that creates hundreds and hundreds off on-screen messages, burying potential errors.

/foss_fim/tools/overlapping_inundation.py:399: RuntimeWarning: invalid value encountered in cast nan_tile = np.array([np.nan]).astype(dtype)[0].

I recommend we branch off of 1217 and fix this so they are merged together.

[mluck]

This seems to have originated here: numpy/numpy#21437

[RobHanna-NOAA]

Needs the following fix:
Changing line 399 in tools/overlapping_inundation.py to nan_tile = np.array([np.nan]) (removed the .astype(dtype)[0] at the end)