Fixed 19217: PHP8 Error Type NULL (#3666)

• Fixed: 19217 Update Survey.php

$attdescriptiondata = decodeTokenAttributes($this->attributedescriptions ?? '');
change to
$attdescriptiondata = decodeTokenAttributes($this->attributedescriptions ?? []);
In PHP 7 it is a warning
in PHP 8 it's a 500! parameter key() must be an array!!

• Fixed 10217: Update common_helper.php

$aSavedExtraTokenFields = Survey::model()->findByPk($surveyid)->tokenAttributes;
change to:
$aSavedExtraTokenFields = Survey::model()->findByPk($surveyid)->tokenAttributes ?? [];
In PHP 7 it is a warning
in PHP 8 it's a 500! $aSavedExtraTokenFields is not allowed to be NULL anymore! in function array_intersect_key()!

• Update common_helper.php

Corrected code line 2946

• 19217: Update Survey.php

revert back to from ?? [] to ?? '' on line 667

• 19217: Update Survey.php

Extra check on first element of array
If it is not an array set array to NULL

• 19217: Update Survey.php

Final edit after line 667:
Check on array after reset(array)

• 19217: Update Survey.php

And some missing spaces...
this one should pass!!!