fail with better error when there are no matching wnd and wtr dates

[jordansread]

LA doesn't interpolate wind speeds between measurements (for good reason). If inputs have no matching wind and water dates, the Run_LA fails with a rather cryptic error that doesn't let the user know what happened.

[jordansread]

I think this is where the failure happens if dates is empty:

https://github.com/GLEON/Lake-Analyzer/blob/master/Source/Run_LA.m#L495