fix for approve minimum and maximum validator

Author: Karthikeyannhs

src/rules_validation_api/validators/campaign_config_validator.py

@@ -16,7 +16,7 @@ def validate_iterations(cls, iterations: list[Iteration]) -> list[IterationValid
 
     @model_validator(mode="after")
     def validate_approval_minimum_is_less_than_or_equal_to_approval_maximum(self) -> typing.Self:
-        if self.approval_minimum and self.approval_maximum:
+        if self.approval_minimum is not None and self.approval_maximum is not None:
             if self.approval_minimum > self.approval_maximum:
                 msg = f"approval_minimum {self.approval_minimum} > approval_maximum {self.approval_maximum}"
                 raise ValueError(msg)