Disable SubmitButton if message contains only whitespace (#880)
Disable SubmitButton if message contains only whitespace (#880)


nashvail/zulip-mobile,vishwesh3/zulip-mobile,nashvail/zulip-mobile,vishwesh3/zulip-mobile,kunall17/zulip-mobile,nashvail/zulip-mobile,vishwesh3/zulip-mobile,kunall17/zulip-mobile,nashvail/zulip-mobile,kunall17/zulip-mobile,kunall17/zulip-mobile,vishwesh3/zulip-mobile