Prevent obscuring errors when querying pg_catalog

[JAForbes]

What

Ensures if there is any postgres errors when invoking fetchArrayTypes that the original error is not obscured.
I don't have a solid understanding of the internals, so I simply added the missing property. There may be a better way.

How to test

• revoke all on all tables in schema pg_catalog from public;
• Run a simple query in postgres.js, e.g. select 1
• You should get a postgres permissions error

Original Error

Uncaught Exception: TypeError: Cannot read property 'replace' of undefined

Expected Error

PostgresError: permission denied for table pg_type

Fixes #202

[porsager]

Oh cool. Very nice!

The fix looks good, but origin should be created as new Error().stack

[JAForbes]

Ah great! I'll push a fix.

[porsager]

Looks good. Would you mind updating to work with #204 merged?

[JAForbes]

Is that right?

[porsager]

It's great - thanks :)