BUG/MINOR: startup: usage() when no -cc arguments

Exit correctly with usage() instead of segfaulting when no argument
were passed to -cc.

Must be backported in 2.5.
diff --git a/src/haproxy.c b/src/haproxy.c
index ec40a64..266f555 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -1943,9 +1943,13 @@
 
 		char *args[MAX_LINE_ARGS+1];
 		int arg = sizeof(args) / sizeof(*args);
-		size_t outlen = strlen(check_condition) + 1;
+		size_t outlen;
 		char *w;
 
+		if (!check_condition)
+			usage(progname);
+
+		outlen = strlen(check_condition) + 1;
 		err = parse_line(check_condition, check_condition, &outlen, args, &arg,
 		                 PARSE_OPT_ENV | PARSE_OPT_WORD_EXPAND | PARSE_OPT_DQUOTE | PARSE_OPT_SQUOTE | PARSE_OPT_BKSLASH,
 		                 &errptr);