Fixes #940

After evaluating a few alternatives, this one performed reliably on all my components.

• If onServerPrefetch the query is not enabled or prefetch is disabled, resolve firstResult
• If start is cancelled and a firstResult is pending, resolve firstResult
• If stop is called and firstResult is pending, resolve firstResult

The remaining cases are coverd with the old conditions.

• If query returns an error and firstResult is pending, reject with firstReject
• If query completes successfully and firstResult is pending, resolve firstResult