chore: disable back button on a conditional expression

- to support disabling navigation on fetch loading

packages/client/src/views/RegisterForm/RegisterForm.tsx

@@ -1115,6 +1115,7 @@ class RegisterFormView extends React.Component<FullProps, State> {
                             type="tertiary"
                             size="small"
                             onClick={this.props.goBack}
+                            disabled={!canContinue}
                           >
                             <Icon name="ArrowLeft" size="medium" />
                             {intl.formatMessage(buttonMessages.back)}