BUG/MINOR: spoe: Fix parsing of arguments in spoe-message section

The array of pointers passed to sample_parse_expr was not really an array but a
pointer to pointer. So it can easily lead to a segfault during the configuration
parsing.
diff --git a/src/flt_spoe.c b/src/flt_spoe.c
index 88f782f..f5918dc 100644
--- a/src/flt_spoe.c
+++ b/src/flt_spoe.c
@@ -2947,8 +2947,9 @@
 				arg->name_len = delim - args[cur_arg];
 				delim++;
 			}
-
-			arg->expr = sample_parse_expr(&delim, &idx, file, linenum, &errmsg, &curproxy->conf.args);
+			arg->expr = sample_parse_expr((char*[]){delim, NULL},
+						      &idx, file, linenum, &errmsg,
+						      &curproxy->conf.args);
 			if (arg->expr == NULL) {
 				Alert("parsing [%s:%d] : '%s': %s.\n", file, linenum, args[0], errmsg);
 				err_code |= ERR_ALERT | ERR_FATAL;