Transactions: QueryMode KV insert fails when parsing result

When a`TransactionAttemptContext` enters QueryMode (i.e. after a query has been issued in the ctx), KV operations are converted into N1QL. When a QueryMode insert operation returns the resulting `TransactionGetResult`, the result does not contain content which is causing the SDK to have an uncaught `SyntaxError: Unexpected end of JSON input` error when the SDK tries to translate the result (see code here).

Tasks:

• The SDK should only try to parse the content if the content exists.
• Add tests to confirm KV operations w/in QueryMode operate as intended.