#248 ReadProperty-IP.vts test 1f fails and a bad error message.

[Buddy Lott]

When running test 1f in ReadProperty-Ip.vts using the
object-list from the device object, the test fails
because VST is expecting an OBJECT_ID to return for
element 0 of the array. An unsigned int is returned
for element 0. Line 4939 of BACnet.Cpp is hit, which
should trigger a better error message to the user.