Decimal place inconsistency occurs in the Top Hosts widget when using the 'avg' aggregation.

When using MySQL DB, 4 digits after comma are displayed, but with PostgreSQL, a lot more digits are displayed after comma. 

Steps to reproduce:

Conditions : PostgreSQL database.

1. create a host;
2. add Zabbix trapper item to this host, item type - Numeric(unsigned);
3. send any value to the item;
4. create a top hosts widget;
5. add a column with created item;
6. add aggregation function 'avg' to this column;
7. save the widget and observe that when you hover over the result in the top hosts widget, approximately 20 digits are shown after the decimal point in the hintbox:

Note: This issue cannot be reproduced, if MySQL database is used