How to get yup.string() to require string of any length greater than 3 or empty

i want to update a list of field data with formik.
i have this validation

validationSchema: Yup.object().shape({
      password: Yup.string()
        .min(4, 'Password must be at least 4 characters.')
        .required('Password must be at least 4 characters.'),
      ....
    }),

i want the user to be able to set password at least a length of 4 and if the user does not enter password then submit as empty string.
password component

<FormControl
              fullWidth
              error={Boolean(formik.touched.password && formik.errors.password)}
              variant="outlined"
            >
              <InputLabel htmlFor="password">Password</InputLabel>
              <OutlinedInput
                id="password"
                name="password"
                inputProps={{
                  autoComplete: 'password',
                  form: {
                    autoComplete: 'off',
                  },
                }}
                type={showPassword ? 'text' : 'password'}
                onBlur={formik.handleBlur}
                onChange={formik.handleChange}
                value={formik.values.password}
                endAdornment={
                  <InputAdornment position="end">
                    <IconButton
                      aria-label="toggle password visibility"
                      onClick={() => setShowPassword(!showPassword)}
                      onMouseDown={(event) => event.preventDefault()}
                      edge="end"
                    >
                      {showPassword ? <VisibilityOff /> : <Visibility />}
                    </IconButton>
                  </InputAdornment>
                }
                label="Password"
              />
              {formik.errors.password && <FormHelperText>{formik.errors.password}</FormHelperText>}
            </FormControl>

but with this code, if the password field is touched but not entered any password formik is not letting to submit the data. how can I do that? thank u in advance.