fix cache bug (Eoghan Sherry)

src/libventi/cache.c

diff --git a/src/libventi/cache.c b/src/libventi/cache.c
index 796d834..24cb8c2 100644
--- a/src/libventi/cache.c
+++ b/src/libventi/cache.c
@@ -510,6 +510,7 @@
 	case BioVenti:
 /*if(b->addr != NilBlock) print("blockput %d\n", b->addr); */
 		b->used = c->now++;
+		/* fall through */
 	case BioVentiError:
 		heapins(b);
 		break;
@@ -541,6 +542,7 @@
 	memmove(b->score, score, VtScoreSize);
 
 	qlock(&c->lk);
+	b->addr = NilBlock;	/* now on venti */
 	b->iostate = BioVenti;
 	h = (u32int)(score[0]|(score[1]<<8)|(score[2]<<16)|(score[3]<<24)) % c->nhash;
 	b->next = c->hash[h];