Fix create stream failing
Fix create stream failing

A change that returned -1 instead of undefined for streamId
messed up the UI logic and it always tried to update a stream
even a non existing one wiht ID of -1.

Fixes #2288

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile