s-s-d: Do not set changegroup unconditionally

Commit 3db7a6eb4fd16b4cea475009bd80be3a41ada014 would always set
changegroup in the --chuid option, even if no colon is given on the
commandline.

[guillem@debian.org:
 - Avoid an else from a fatal if. ]

Signed-off-by: Guillem Jover <guillem@debian.org>

utils/start-stop-daemon.c

@@ -1038,10 +1038,11 @@ parse_options(int argc, char * const *argv)
 			 * argument later. */
 			changeuser_len = strcspn(optarg, ":");
 			changeuser = xstrndup(optarg, changeuser_len);
-			if (optarg[changeuser_len] == ':' &&
-			    optarg[changeuser_len + 1] == '\0')
-				fatal("missing group name");
-			changegroup = optarg + changeuser_len + 1;
+			if (optarg[changeuser_len] == ':') {
+				if (optarg[changeuser_len + 1] == '\0')
+					fatal("missing group name");
+				changegroup = optarg + changeuser_len + 1;
+			}
 			break;
 		case 'g':  /* --group <group>|<gid> */
 			changegroup = optarg;