Steps to reproduce:
1. create a trap item with a floating point data type and a Custom multiplier of -1
2. reload configuration cache
3. send a value of 5 to this item

Result:
On the "Latest data" screen, we see -5 – this is the expected value.

4. change the data type of this item to unsigned integer
5. reload configuration cache
6. send a value of 5 to this item

Result:
On the "Latest data" screen, we see an error. Zero is expected without any errors.

Value of type "double" is not suitable for value type "Numeric (unsigned)". Value "-5"

7. stop Zabbix server
8. start Zabbix server
9. send a value of 5 to this item

Result:
On the "Latest data" screen, we see 0 without any errors.