file_get_contents(public:/...): failed to open stream: "DrupalPublicStreamWrapper::stream_open" call failed; filesize(): stat failed for public://...; SQLSTATE[HY000]: General error: 1366 Incorrect integer value: '' for column 'filesize'

Backtrace A

2	advagg_scan_for_changes	96	sites/all/modules/advagg/advagg.cache.inc
1	advagg_get_info_on_files	34	sites/all/modules/advagg/advagg.cache.inc
0	file_get_contents	455	sites/all/modules/advagg/advagg.inc

Backtrace B

4	advagg_scan_for_changes	96	sites/all/modules/advagg/advagg.cache.inc
3	advagg_get_info_on_files	34	sites/all/modules/advagg/advagg.cache.inc
2	drupal_alter	501	sites/all/modules/advagg/advagg.inc
1	advagg_advagg_get_info_on_files_alter	1135	includes/module.inc
0	file_get_contents	249	sites/all/modules/advagg/advagg.advagg.inc

Also got

filesize(): stat failed for public://...

from the same code path.

All of this resulted in a WSOD due to a PDO expection

SQLSTATE[HY000]: General error: 1366 Incorrect integer value: '' for column 'filesize' at row 1: UPDATE {advagg_files} SET content_hash=:db_update_placeholder_0, filesize=:db_update_placeholder_1, mtime=:db_update_placeholder_2, linecount=:db_update_placeholder_3, changes=:db_update_placeholder_4, filename_hash=:db_update_placeholder_5
WHERE ( (filename_hash = :db_condition_placeholder_0) ); Array
(
    [:db_update_placeholder_0] => 47DEQpj8HBSa-_TImW-5JCeuQeRkm5NMpJWZG3hSuFU
    [:db_update_placeholder_1] => 
    [:db_update_placeholder_2] => 
    [:db_update_placeholder_3] => 0
    [:db_update_placeholder_4] => 498
    [:db_update_placeholder_5] => 6hIjGgzXAHXKK0zi9XBpx5Jp2Xdi1V5QqtoY74tkp3c
    [:db_condition_placeholder_0] => 6hIjGgzXAHXKK0zi9XBpx5Jp2Xdi1V5QqtoY74tkp3c
)

And this backtrace

2	advagg_push_new_changes	873	sites/all/modules/advagg/advagg.admin.inc
1	advagg_insert_update_files	119	sites/all/modules/advagg/advagg.cache.inc
0	execute	227	sites/all/modules/advagg/advagg.inc