Teams lose field values if field_ui is enabled/disabled

[audave]

Description

To replicate

• Start With core field_ui module enabled
• add some fields to the Team entity.
• Create/edit a team and add a value to the newly created field.
• View team -> value should present
• Disable field_ui module
• view team -> field value has vanished
• Re-enable field_ui module
• view team -> field value has reappeared

Below is the offending code:
$this->config->get('field_ui.settings')->get('field_prefix');
Returns a different value depending if field_ui is enabled.

` /**

• Returns the field UI's field name prefix.
• @return string
• Prefix of the field.
  */
  protected function getFieldPrefix(): string {
  return (string) $this->config->get('field_ui.settings')->get('field_prefix');
  }`

[shishir-intelli]

@audave
When we uninstall the field_ui module, NULL is passed to prefix which was causing this issue,
PR 988 will fix this issue.
Let me know if the issue is not resolved with the above PR.

[audave]

I've put a comment on #988 (comment)