I have a hotfix for it.
Open Sources/Gallery.php
Around line 3196 in function RecountFileQuotaTotals
Find
mysql_free_result($dbresult2);
//Update the quota
db_query("UPDATE {$db_prefix}gallery_userquota SET totalfilesize = $total WHERE ID_MEMBER = " . $row['ID_MEMBER'] . " LIMIT 1", __FILE__, __LINE__);
Change to
if($total == '')
$total = 0;
mysql_free_result($dbresult2);
//Update the quota
db_query("UPDATE {$db_prefix}gallery_userquota SET totalfilesize = $total WHERE ID_MEMBER = " . $row['ID_MEMBER'] . " LIMIT 1", __FILE__, __LINE__);