How to use reject correctly?

"files[]?": type("File | File[] < 6").narrow((data, ctx) => {
    const MAX_SIZE = 4 * 1024 * 1024;

     if (Array.isArray(data)) {
    const totalSize = data.reduce((sum, file) => sum + file.size, 0);
    if (totalSize > MAX_SIZE) {
      return ctx.reject({
        message: `Total files size should be less than 4MB (actual: ${(totalSize/1024/1024).toFixed(2)}MB)`,
        actual: `${data.length} files, ${totalSize} bytes total`,
      });
    }
    return true;
  }
  
  if (data.size > MAX_SIZE) {
    return ctx.reject({
      message: "File size should be less than 4MB",
      actual: `${(data.size/1024/1024).toFixed(2)}MB`,
    });
  }
  
  return true;
  }),

TypeError: Cannot read properties of undefined (reading 'name')
    at Object.description (webpack-internal:///(rsc)/../../node_modules/@ark/schema/out/predicate.js:23:67)
    at implementation.defaults.expected (webpack-internal:///(rsc)/../../node_modules/@ark/schema/out/shared/implement.js:107:39)
    at get expected [as expected] (webpack-internal:///(rsc)/../../node_modules/@ark/schema/out/shared/errors.js:63:47)
    at eval (webpack-internal:///(rsc)/../../node_modules/@ark/schema/out/roots/union.js:89:101)
    at Array.forEach (<anonymous>)
    at eval (webpack-internal:///(rsc)/../../node_modules/@ark/schema/out/roots/union.js:86:24)
    at Array.map (<anonymous>)
    at expected (webpack-internal:///(rsc)/../../node_modules/@ark/schema/out/roots/union.js:84:61)
...