freedreno/a6xx: Fix fd6_draw_vbo() return

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6649>
diff --git a/src/gallium/drivers/freedreno/a6xx/fd6_draw.c b/src/gallium/drivers/freedreno/a6xx/fd6_draw.c
index 3e9ec98..284569f 100644
--- a/src/gallium/drivers/freedreno/a6xx/fd6_draw.c
+++ b/src/gallium/drivers/freedreno/a6xx/fd6_draw.c
@@ -208,7 +208,7 @@
 
 	/* bail if compile failed: */
 	if (!fd6_ctx->prog)
-		return NULL;
+		return false;
 
 	fixup_draw_state(ctx, &emit);