Several error messages on activation

Hi,
I love your plugin. I’ve activated it on a new site (not live yet), and I get a LOT of error notifications. I’ve reverted to 2017 theme and disabled all other plugins, and I still get the same errors. I have debug display on right now. I know I can hide those errors, but I’d rather use plugins that are notice/error-free.

Here are the notices that appear on my screen whilst only your plugin is activated with 2017 theme activated, WP version 4.9.5:

The plugin generated 607 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

Deprecated: Non-static method WPVC_Map_Widget::load_widget() should not be called statically in /[***]/wp-includes/class-wp-hook.php on line 286

Deprecated: Non-static method WPVC_Master::init() should not be called statically in /[***]/wp-includes/class-wp-hook.php on line 286

Deprecated: Non-static method WPVC_Master::add_pages() should not be called statically in /[***]/wp-includes/class-wp-hook.php on line 286

Notice: Undefined index: hex_smap_button in /[***]/wp-content/plugins/wp-visited-countries-reloaded/inc/class-wpvc-settings.php on line 536

Notice: Undefined index: pos_smap_button in /[***]/wp-content/plugins/wp-visited-countries-reloaded/inc/class-wpvc-settings.php on line 537

Deprecated: Non-static method WPVC_Master::admin_notice() should not be called statically in /[***]/wp-includes/class-wp-hook.php on line 286

I realize this is a free plugin so you probably don’t work on it much, but do you have any plans on fixing the deprecated code in the near future?

Thanks in advance,
Caro