Cannot set the default helperText for Select components in theme

Describe the bug Of course, vanilla mui Select elements do not have helperText; you have to add a FormHelperText to your form control with the helper text as a child. But setting props.MuiFormHelperText.children='default helper text' in my theme only changes the helper text for vanilla FormHelperTexts.

This is necessary because I want to set the helper text to a space ' ' to prevent form resizing, e.g. when a field has error helper text.

To Reproduce Steps to reproduce the behavior:

1. Go to this forked sandbox
2. Search for the comment: // HERE: Try commenting the following line. The helper text
3. … And comment the following line 😃

The additions I made are roughly…

import {
  // ...
  FormControl,
  InputLabel,
  Select as MuiSelect,
  MenuItem,
} from '@material-ui/core'

// ...

const theme = createMuiTheme({
  props: {
    // ...
    MuiFormHelperText: {
      children: 'This should be the default helper text of all Select components',
    },
})

// ...

// In the render function of MainForm
  const formFields = [
    // Default helper text doesn't work here
    <Select
      label="Pick some cities..."
      name="cities"
      required={required.cities}
      data={selectData}
      multiple={true}
      // HERE: Try commenting the following line. The helper text
      helperText="Woah helper text"
    />,
    // Default helper text works here
    <FormControl>
      <InputLabel id="demo">Cities</InputLabel>
      <MuiSelect labelId="demo" fullWidth>
        {selectData.map(({ label, value }) => (
          <MenuItem value={value}>{label}</MenuItem>
        ))}
      </MuiSelect>
      <FormHelperText>{/* Insert helper text here */}</FormHelperText>
    </FormControl>,
  ];

I also removed most of the form components to simplify the example.

Expected behavior Commenting out the line indicated should change the select helperText to 'This should be the default helper text of all Select components'.

Additional context This ‘bug’ is not a super high priority, but it would help with theming.

[lookfirst]

Closing, seems to be a non-issue now.

[nmay231]

Example repo