fix dashboard/my/collections when default admin set table doesn’t exist

app/services/hyrax/admin_set_create_service.rb

@@ -118,7 +118,12 @@ def find_default_admin_set
         return if id.blank?
         Hyrax.query_service.find_by(id: id)
       rescue Valkyrie::Persistence::ObjectNotFoundError
-        # id is saved but doesn't exist
+        # The default ID is DEFAULT_ID when saving is not supported.  It is ok
+        # for this default id to be known but not found.  The admin set will be
+        # created with DEFAULT_ID by find_or_create_default_admin_set.
+        return unless save_default?
+
+        # id is saved in the default_admin_set_persister's table but doesn't exist
         # NOTE: This is a corrupt state and shouldn't happen.  Manual intervention
         #       is required to determine the correct value for the default admin
         #       set id.  The saved id either needs to be updated to the correct
@@ -142,7 +147,7 @@ def find_unsaved_default_admin_set
       # @return [String | nil] the default admin set id; returns nil if not set
       # @note For general use, it is better to use `Hyrax.config.default_admin_set_id`.
       def default_admin_set_id
-        DEFAULT_ID unless save_default?
+        return DEFAULT_ID unless save_default?
         id = default_admin_set_persister.first&.default_admin_set_id
         id = find_unsaved_default_admin_set&.id&.to_s if id.blank?
         id

spec/services/hyrax/admin_set_create_service_spec.rb

@@ -43,6 +43,14 @@
       end
     end
 
+    context "and Hyrax::DefaultAdministrativeSet table does not exist" do
+      before { allow(Hyrax::DefaultAdministrativeSet).to receive(:save_supported?).and_return(false) }
+      it "creates a default admin set with the DEFAULT_ID" do
+        expect(Hyrax::DefaultAdministrativeSet).not_to receive(:first)
+        expect(described_class.find_or_create_default_admin_set.id).to eq described_class::DEFAULT_ID
+      end
+    end
+
     context "when default admin set id is NOT saved in the database" do
       before { allow(Hyrax::DefaultAdministrativeSet).to receive(:count).and_return(0) }
       context "but default admin set does exist" do