dos2unix: fix the case w/o parameters

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

coreutils/dos2unix.c

@@ -92,7 +92,7 @@ int dos2unix_main(int argc UNUSED_PARAM, char **argv)
 	do {
 		/* might be convert(NULL) if there is no filename given */
 		convert(*argv, conv_type);
-	} while (*++argv);
+	} while (*argv && *++argv);
 
 	return 0;
 }