how to use validation-messages ?

[yogendrarr]

In my case,
Below is i am checking photo size if size greter than my provided size then it should return message . so its working fine.
but if file is valid, then it should not show the else custom messege how to do that kind of validations.
i need to forcefully need to return in else part, how to avoid this.
<FormKit validation-visibility="blur" ref="uploadInput" type="file" label="Candidate Photograph" name="photograph" v-model="photograph.file" help="Please upload your photograph" :accept="photograph.mimeType" :validation="[...(isMandatory ? [['required'], ['is']] : [])]" :validation-messages="{ required: 'photograph is required', is: customMessage, }" />

` const customMessage = ({ node }) => {
if (photograph.file !== null) {
let size = node.value[0].file.size / 1000;

    if (size < photograph.minSize || size > photograph.maxSize) {
      return `${node.value[0].file.name} size should be between ${photograph.minSize} to ${photograph.maxSize}.`;
    } 
    else {
      selectFile(photograph.file);
      return '  ';
    }
  }
};`