TopologySummary raises exception on missing schema

[strk]

I think TopologySummary function should never raise an exception. It does if the named schema does not exist. If the topology name is found in topology.topology but the schema is missing it raises:

ERROR:  Got relation "topotest.relation" does not exist (42P01)

If there's not even a record in topology.topology it raises:

ERROR:  Got query string argument of EXECUTE is null (22004)

This is with PostgreSQL 9.3.4, dunno if it was different before (as I'm pretty sure I made some effort to avoid these cases)

[strk]

Fixed with r13186 in trunk, will wait for bot builds before backporting to 2.1

[strk]

Debbie and Travis were happy, so am I. Backported to 2.1 branch with r13187