_wpnonce error

We are getting the following error messages

Undefined index: key in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-image-upload.php on line 28
Undefined index: timestamp in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-image-upload.php on line 29
Undefined index: _wpnonce in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-image-upload.php on line 30
Undefined index: set_id in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-image-upload.php on line 32
Undefined index: set_mode in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-image-upload.php on line 33
Undefined index: _wpnonce in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-file-upload.php on line 29
Undefined index: key in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-file-upload.php on line 30
Undefined index: timestamp in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-file-upload.php on line 31
Undefined index: set_id in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-file-upload.php on line 33
Undefined index: set_mode in /hsphere/local/home/ncbahost/national-cba.co.uk/wp-content/plugins/ultimate-member/core/lib/upload/um-file-upload.php on line 34

It appears to be a result of someone in Korea attempting to access the module directly without being logged on. Could you handle the error in a more graceful way?