Masterbar: PHP Notices when using the AMP plugin

[jeherve]

Steps to reproduce the issue

1. Add the AMP plugin to your site.
2. In the plugin options, switch to the "Native" option.
3. Go to Jetpack > Settings > Writing and enable the Masterbar

( ! ) Notice: Trying to get property 'post_type' of non-object in /home/dereksma/public_html/wp-content/plugins/amp/includes/class-amp-post-type-support.php on line 80

( ! ) Notice: Trying to get property 'ID' of non-object in /home/dereksma/public_html/wp-content/plugins/amp/includes/class-amp-post-type-support.php on line 101

Possible fix: #10945 (comment)

This will also require this PR from the AMP end:
ampproject/amp-wp#1794

[westonruter]

This will also require this PR from the AMP end:
ampproject/amp-wp#1794

This AMP plugin PR is not required. It merely will issue the _doing_it_wrong() which will guide Jetpack and other plugins to make the switch to the wp action in the first place.