BUG/MAJOR: stats: correctly check for a possible divide error when showing compression ratios

Commit 5730c68b changed to display compression ratios based on 2xx
responses, but we should then check that there are such responses
instead of checking for requests. The risk is a divide error if there
are some requests but no 2xx yet (eg: redirect).
diff --git a/src/dumpstats.c b/src/dumpstats.c
index 7cc5911..f2849ef 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -2477,7 +2477,7 @@
 					chunk_appendf(&trash, " other=%lld,", px->fe_counters.p.http.rsp[0]);
 					chunk_appendf(&trash, " compressed=%lld (%d%%)",
 					              px->fe_counters.p.http.comp_rsp,
-					              px->fe_counters.p.http.cum_req ?
+					              px->fe_counters.p.http.rsp[2] ?
 					              (int)(100*px->fe_counters.p.http.comp_rsp/px->fe_counters.p.http.rsp[2]) : 0);
 					chunk_appendf(&trash, " intercepted=%lld\"", px->fe_counters.intercepted_req);
 				}
@@ -3218,7 +3218,7 @@
 					chunk_appendf(&trash, " other=%lld ", px->be_counters.p.http.rsp[0]);
 					chunk_appendf(&trash, " compressed=%lld (%d%%)\"",
 					              px->be_counters.p.http.comp_rsp,
-					              px->be_counters.p.http.cum_req ?
+					              px->be_counters.p.http.rsp[2] ?
 					              (int)(100*px->be_counters.p.http.comp_rsp/px->be_counters.p.http.rsp[2]) : 0);
 				}