Using version 1.6.0 I can reproduce the fatal error by simply editing a text page from the external view. This is the resulting message:
Fatal error: Uncaught TypeError: array_intersect_key(): Argument #1 ($array) must be of type array, string given in /home/insider/chocolatedetective.co.uk/wp-includes/rest-api/class-wp-rest-server.php:1411 Stack trace: #0 /home/insider/chocolatedetective.co.uk/wp-includes/rest-api/class-wp-rest-server.php(1411): array_intersect_key('name', Array) #1 /home/insider/chocolatedetective.co.uk/wp-includes/rest-api/class-wp-rest-server.php(1333): WP_REST_Server->get_data_for_route('/wplikeapro-sen...', Array, 'view') #2 /home/insider/chocolatedetective.co.uk/wp-includes/rest-api/class-wp-rest-server.php(1223): WP_REST_Server->get_data_for_routes(Array, 'view') #3 /home/insider/chocolatedetective.co.uk/wp-includes/rest-api/class-wp-rest-server.php(1139): WP_REST_Server->get_index(Object(WP_REST_Request)) #4 /home/insider/chocolatedetective.co.uk/wp-includes/rest-api/class-wp-rest-server.php(985): WP_REST_Server->respond_to_request(Object(WP_REST_Request), '/', Array, NULL) #5 /home/insider/chocolatedetective.co.uk/wp-includes/rest-api.php(479): WP_REST_Server->dispatch(Object(WP_REST_Request)) #6 /home/insider/chocolatedetective.co.uk/wp-includes/rest-api.php(2810): rest_do_request(Object(WP_REST_Request)) #7 [internal function]: rest_preload_api_request(Array, '/') #8 /home/insider/chocolatedetective.co.uk/wp-admin/edit-form-blocks.php(82): array_reduce(Array, 'rest_preload_ap...', Array) #9 /home/insider/chocolatedetective.co.uk/wp-admin/post.php(187): require('/home/insider/c...') #10 {main} thrown in /home/insider/chocolatedetective.co.uk/wp-includes/rest-api/class-wp-rest-server.php on line 1411
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