freedreno: allow ctx->batch to be NULL
This was mostly true already, now that we use fd_context_batch()
for
first access to batch in draw/clear/grid paths. So we can drop the old
code in batch_flush()
that tried to prevent ctx->batch
from being
NULL.
Fixes a crash with a large number of tabs in chromium.
Cc: "20.0" mesa-stable@lists.freedesktop.org Signed-off-by: Rob Clark robdclark@chromium.org