draw: emit so primitives before ending empty pipeline.

There may be non-stream 0 emitted primitives that have to be processed.

Fixes:
KHR-GL42.transform_feedback_overflow_query_ARB.multiple-streams-one-buffer-per-stream
KHR-GL42.transform_feedback_overflow_query_ARB.multiple-streams-multiple-buffers-per-stream

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5555>
1 file changed