fix(typescript): avoid parsing empty messageTerminators in JSON stream case.

[eyw520]

Description

Our Stream.ts logic currently breaks when the JSON event stream ends in a messageTerminator, leading to an empty string that, when parsed as JSON, results in a parse error.

This fix 1) better checks for complex messageTerminator patterns and 2) performs a better check for empty lines.

Changes Made

• Update Stream.ts with two changes to parsing logic.

Testing

• Unit tests added/updated
• Manual testing completed