Variable USSP_WN is not initialized for full array

[JessicaMeixner-NOAA]

Describe the bug
The variable USSP_WN is not initialized in model/src/w3gridmd.F90 before being written to mod_def. Most compilers initlized to zero so it has gone undetected so far. Moreover, it is initialized for the part of the array that is actually used in the code, so it's a non-issue other than ensuring reproducible on machines where the uninitialized part is randomly assigned.

To Reproduce
Find a compiler/debug option that initliaizes variables to random values, use ASCII output to print out values mod_defs and you will note that USSP_WN is not bit-for-bit between runs and a cause of mod_defs not being reproducible.

Expected behavior
Mod_defs should be reproducible between runs.

Additional context
A fix is coming soon...