This warning occurs when value is not specified for an attribute where the value specification is not mandatory. %s - attribute name.
Provide the sub-attributes or remove the line of code if not required.
Example
[#Menu: Gateway Of Tally]
Add: Item: "MyReport": Display: MyReport
[Report: MyReport]
Use : Balance Sheet
Form :
In the above example, the value is not specified for the sub-attribute Form. Hence the message, warning T0010: The value of the attribute 'Form:' is empty.
The code is corrected by removing the attribute Form:
[#Menu: Gateway Of Tally]
Add: Item: "MyReport": Display: MyReport
[Report: MyReport]
Use : Balance Sheet