Error in debug.log file

I’m not able to reproduce this, and I see no syntax error in the code. There is a dot preceding a line break here, in the middle of a long property declaration. That should not be a problem tho.

What Server / PHP are you running?

It seems to be a limitation of PHP 5.5, which is the version installed in my server: before PHP 5.6.0, you could not declare a class member variable using concatenations, according to:
https://www.php.net/manual/en/language.oop5.properties.php
This subject was also related on these posts:
https://stackoverflow.com/questions/37988721/string-concatenation-with-constants
https://stackoverflow.com/questions/21941824/class-variable-declaration
As it results in a fatal error (my browser’s window became completely white), I suggest you the following modification in line 34:
public $eeNotifyMessageDefault = "Greetings,\r\nYou should know that a file has been uploaded to your website.\r\n[file-list]\r\n";
I did that and could install your plugin afterwards.

Okay, that makes sense. Unfortunately, I can’t fix this for you. Please update your PHP to a version supported by WordPress.

Alternatively, you can keep the fix on your side and either rename the plugin or don’t update it.