BUG/MEDIUM: http: fix the url_param fetch

The "name" and "name_len" arguments in function "smp_fetch_url_param"
could be left uninitialized for subsequent calls.

[wt: no backport needed, this is an 1.6 regression introduced by
 commit 4fdc74c ("MINOR: http: split the url_param in two parts") ]

diff --git a/src/proto_http.c b/src/proto_http.c
index fa3be6a..3d41c56 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -11762,22 +11762,22 @@
 	const char *name;
 	int name_len;
 
-	if (!smp->ctx.a[0]) { // first call, find the query string
-		if (!args ||
-		    (args[0].type && args[0].type != ARGT_STR) ||
-		    (args[1].type && args[1].type != ARGT_STR))
-			return 0;
+	if (!args ||
+	    (args[0].type && args[0].type != ARGT_STR) ||
+	    (args[1].type && args[1].type != ARGT_STR))
+		return 0;
 
-		if (args[1].type)
-			delim = *args[1].data.str.str;
+	name = "";
+	name_len = 0;
+	if (args->type == ARGT_STR) {
+		name     = args->data.str.str;
+		name_len = args->data.str.len;
+	}
 
-		name = "";
-		name_len = 0;
-		if (args->type == ARGT_STR) {
-			name     = args->data.str.str;
-			name_len = args->data.str.len;
-		}
+	if (args[1].type)
+		delim = *args[1].data.str.str;
 
+	if (!smp->ctx.a[0]) { // first call, find the query string
 		CHECK_HTTP_MESSAGE_FIRST();
 
 		msg = &smp->strm->txn->req;