How to set Character value for all entries in CT04

I am creating a characteristic for Contract Agreement to be used in my PR Release Strategy but I am unable to find a value which will accept all contracts. I have to trigger my Release on whether the Contract field in PR is filled or not. Leaving it empty resolves the not filled option but cannot find a solution to cover the contract field filled case.The type of the characteristic is Character in structure CEBAN with field name KONNR.