Notice: Location permalink error in multisite

I’ve started getting notices in the event admin listing.

Notice: Trying to get property of non-object in (redacted)/wp-includes/link-template.php on line 284
Call Stack
#	Time	Memory	Function	Location
1	0.0006	357416	{main}( )	.../edit.php:0
2	1.2542	86404736	WP_List_Table->display( )	.../edit.php:362
3	1.2932	86528408	WP_List_Table->display_rows_or_placeholder( )	.../class-wp-list-table.php:1097
4	1.2932	86528512	WP_Posts_List_Table->display_rows( )	.../class-wp-list-table.php:1165
5	1.2932	86529688	WP_Posts_List_Table->_display_rows( )	.../class-wp-posts-list-table.php:641
6	1.3540	86995408	WP_Posts_List_Table->single_row( )	.../class-wp-posts-list-table.php:659
7	1.3563	86995728	WP_List_Table->single_row_columns( )	.../class-wp-posts-list-table.php:1195
8	1.4022	87003256	WP_Posts_List_Table->column_default( )	.../class-wp-list-table.php:1254
9	1.4023	87003408	do_action( )	.../class-wp-posts-list-table.php:1162
10	1.4023	87003984	WP_Hook->do_action( )	.../plugin.php:453
11	1.4023	87004032	WP_Hook->apply_filters( )	.../class-wp-hook.php:310
12	1.4023	87004704	call_user_func_array:{(redacted)/wp-includes/class-wp-hook.php:286} ( )	.../class-wp-hook.php:286
13	1.4023	87005128	EM_Event_Posts_Admin::columns_output( )	.../class-wp-hook.php:286
14	1.4092	87023384	EM_Location->get_permalink( )	.../em-event-posts-admin.php:218
15	1.4098	87023432	get_post_permalink( )	.../em-location.php:701

This is a WordPress multi-site installation. Locations were not set to be on the main blog initially. After some locations were added, I changed this option to put locations on the main blog. I believe these notices only happen on events that have locations previously assigned before I switched the option.