fix value parsing

contracts/forms.py

@@ -35,6 +35,7 @@ class SingnatureRepresentativeFormSet(BaseInlineFormSet):
                     attempted_signature_position.isnumeric()
                     and key.startswith("contractee_signatures-")
                     and key.endswith("-id")
+                    and value.isnumeric()
                 ):
                     signature_position = int(attempted_signature_position)
                     signature_id = int(value)