Add missing nullability checks during data retrieval

[EitanBlumin]

Several data retrieval calls could potentially throw an error if the data column is NULL.
A nullability check should be added to avoid this and/or create an informative error message.

sql-clr-ics/sql_clr_ics/clr_send_ics_invite.cs

Line 140 in dea8c46

if (reply_to.IsNull) reply_to = rdr.GetSqlString(1);

[EitanBlumin]

Hi @twells-fi , please try checking version 2.4 which I committed here:

https://github.com/MadeiraData/sql-clr-ics/blob/v2.4/sql_clr_ics/sql_clr_ics_install.sql

Let me know if it works better for you.