Fix memory leak in get_cfg

When setting --shadow-exclude-reg from both the config file and the
command line, one of the strings is not freed.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/options.c

@@ -722,6 +722,7 @@ void get_cfg(options_t *opt, int argc, char *const *argv, bool shadow_enable,
 			break;
 		case 305:
 			// --shadow-exclude-reg
+			free(opt->shadow_exclude_reg_str);
 			opt->shadow_exclude_reg_str = strdup(optarg);
 			log_warn("--shadow-exclude-reg is deprecated. You are likely "
 			         "better off using --shadow-exclude anyway");