ODBGet("/non_existant_odb_entry") caused ODB corruption requiring ODB reload from backup file.
It turns out that ODBGet() tries to create ODB entries if they do not already exist, but because ODBGet() was
called without the "type", "length", etc arguments, the mhttpd "jset" command was issued with "type" set to
zero. This resulted in a db_create_key() call with "type" set to zero which created an invalid ODB entry.
odb.c rev 4829 adds a check for "type<=0" (check for "type>=TID_LAST" was already there).
In addition, mhttpd.c rev 4830 adds a "jset" check for type==0.