Fixes a promise warning

[lelandcope]

Fixes a promise warning because nothing is being returned.

Actual message: Warning: a promise was created in a handler but was not returned from it

Stack Trace

Warning: a promise was created in a handler but was not returned from it
  at process._tickDomainCallback (node.js:486:13)
  at process.wrappedFunction (/Users/leland/Sites/ListReports/portal/node_modules/newrelic/lib/transaction/tracer/index.js:250:51)
From previous event:
  at Promise.wrappedFunction [as _then] (/Users/leland/Sites/ListReports/portal/node_modules/newrelic/lib/transaction/tracer/index.js:225:51)
  at Model.tableReady (/Users/leland/Sites/ListReports/portal/node_modules/thinky/lib/model.js:215:34)
  at Function.Model.new (/Users/leland/Sites/ListReports/portal/node_modules/thinky/lib/model.js:167:11)
  at Thinky.createModel (/Users/leland/Sites/ListReports/portal/node_modules/thinky/lib/thinky.js:130:24)

[neumino]

Hum, I'm not sure you are fixing the appropriate thing.

Thinky is still using bluebird 2.x, so it doesn't warn about this. There's also no promise created where you added a return null