TypeError "Cannot read property 'classList' of null" on Submit

[jankrikava]

Hey there,

first off thanks for this great wp plugin!

I can't get rid of this error (index.js?ver=5.4:formatted:196):

TypeError: Cannot read property 'classList' of null
    at a (index.js?ver=5.4:formatted:150)
    at Array.forEach (<anonymous>)
    at index.js?ver=5.4:formatted:188
(anonymous) @ index.js?ver=5.4:formatted:196
Promise.catch (async)
f @ index.js?ver=5.4:formatted:195
(anonymous) @ index.js?ver=5.4:formatted:464

While submitting an error notification pops up but with no error text:

Once I'm submitting again the submit is successful, the success notification pops up and everything is fine.

Plugins/Themes used:

• Contact Form 7 v5.4
• Contact Form 7 Signature Addon v4.2.2
• The7 v9.9.1 (Theme)

Would appreciate some help or a quick hint. Thanks upfront for the help!

[jankrikava]

Fixed it while reading through the plugin's wordpress.org section.

chloemccarty's solutions worked fine for me:

• https://wordpress.org/support/topic/validation-required-issues/#post-14155577
• https://wordpress.org/support/topic/cf7-5-4-update-missing-validation-message/
  Used both to fix it.

Will leave this ticket open for you to fix it in the repo.