Fix segfault caused by off by one error

src/cmd.cpp

@@ -201,7 +201,7 @@ static constexpr size_t strlen_pre_eq(const char* str){
 
 #define CHECK_VALID_SHORT_ARG(opt, arg, type) \
 	{ \
-		if(next_arg == (argc-1) || !is_##type(arg)){ \
+		if(next_arg == argc || !is_##type(arg)){ \
 			fwprintf(stderr, L"'-%s' requires an argument of type " #type "\n", opt); \
 			ret.error = 1; \
 			break; \