Error when installing from configuration

In my setup I can get rid of the message by declaring the variable with a format I have before the if-statement. But there might be a better way that could work for everyone?

It seems to work, I see the text on the settings page and it shows as Full HTML, but I think that's because I have that value in my configuration.

The formats I have are basic_html and full_html.

Isn't there some way to set some default value for the format, so we can declare the variable and don't get the error message?

I did create a patch for our environment but that will only work for sites with the same format we have.
If anyone else has this problem and finds this issue, then the patch basically looks like this:

diff --git a/eu_cookie_compliance.install b/eu_cookie_compliance.install
index c324a4f..64019e7 100644
--- a/eu_cookie_compliance.install
+++ b/eu_cookie_compliance.install
@@ -91,6 +91,8 @@ function eu_cookie_compliance_install() {
 
   $all_filter_formats = filter_formats(\Drupal::currentUser());
 
+  $default_filter_format = 'basic_html';
+
   if (count($all_filter_formats)) {
     // Determine the best default text format to use.
     $default_filter_format = filter_default_format();

The patch in #8 removes the error message for me.