BUG/MEDIUM: h2: ensure we always know the stream before sending a reset

The recent patch introducing the H2_CS_FRAME_E state to emit stream
resets was not totally correct in that in the rare case where there is
no room left to emit the reset, the next call to process it later could
use an uninitialized stream. This only affects responses to frames that
are sent on closed streams though.

This fix must be backported to 1.8.
1 file changed