BUG/MAJOR: cli/streams: missing unlock on exit "show sess"

An unlock was missing on the situation where the session disappeared
while watching it.
diff --git a/src/stream.c b/src/stream.c
index ddaca39..12545fb 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -3229,6 +3229,7 @@
 
 			if (ci_putchk(si_ic(si), &trash) == -1) {
 				si_applet_cant_put(si);
+				SPIN_UNLOCK(STRMS_LOCK, &streams_lock);
 				return 0;
 			}