BUG/MAJOR: cli: do not dereference strm_li()->proto->name

Or it will crash when dumping streams instanciated by an applet,
like Lua's cosockets.
diff --git a/src/dumpstats.c b/src/dumpstats.c
index fae9e3f..39bdd17 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -6011,8 +6011,7 @@
 			chunk_appendf(&trash,
 				     "%p: proto=%s",
 				     curr_sess,
-				     strm_li(curr_sess)->proto->name);
-
+				     strm_li(curr_sess) ? strm_li(curr_sess)->proto->name : "?");
 
 			conn = objt_conn(strm_orig(curr_sess));
 			switch (conn ? addr_to_str(&conn->addr.from, pn, sizeof(pn)) : AF_UNSPEC) {