Fix validations for user cap setting

ee/app/models/ee/application_setting.rb

@@ -95,11 +95,15 @@ module EE
       validate :allowed_frameworks, if: :compliance_frameworks_changed?
 
       validates :new_user_signups_cap,
-                numericality: { only_integer: true,
-                                allow_nil: true,
-                                greater_than: 0 }
+                allow_blank: true,
+                numericality: { only_integer: true, greater_than: 0 }
       validates :new_user_signups_cap,
-                numericality: { less_than_or_equal_to: proc { License.current&.restricted_user_count } },
+                allow_blank: true,
+                numericality: {
+                  only_integer: true,
+                  greater_than: 0,
+                  less_than_or_equal_to: proc { License.current&.restricted_user_count }
+                },
                 if: proc { License.current&.restricted_user_count? }
 
       after_commit :update_personal_access_tokens_lifetime, if: :saved_change_to_max_personal_access_token_lifetime?

ee/spec/models/application_setting_spec.rb

@@ -88,6 +88,8 @@ RSpec.describe ApplicationSetting do
     it { is_expected.to allow_value(nil).for(:new_user_signups_cap) }
     it { is_expected.to allow_value(1).for(:new_user_signups_cap) }
     it { is_expected.to allow_value(10).for(:new_user_signups_cap) }
+    it { is_expected.to allow_value("").for(:new_user_signups_cap) }
+    it { is_expected.not_to allow_value("value").for(:new_user_signups_cap) }
     it { is_expected.not_to allow_value(-1).for(:new_user_signups_cap) }
     it { is_expected.not_to allow_value(2.5).for(:new_user_signups_cap) }
 
@@ -175,6 +177,7 @@ RSpec.describe ApplicationSetting do
 
       it { is_expected.to allow_value(max_active_user_count - 1).for(:new_user_signups_cap) }
       it { is_expected.to allow_value(max_active_user_count).for(:new_user_signups_cap) }
+      it { is_expected.to allow_value(nil).for(:new_user_signups_cap) }
       it { is_expected.not_to allow_value(max_active_user_count + 1).for(:new_user_signups_cap) }
     end
   end