Add project not found error

ee/app/graphql/mutations/incident_management/oncall_rotation/create.rb

@@ -39,6 +39,8 @@ module Mutations
         def resolve(iid:, project_path:, participants:, **args)
           project = Project.find_by_full_path(project_path)
 
+          raise_project_not_found unless project
+
           schedule = ::IncidentManagement::OncallSchedulesFinder.new(current_user, project, iid: iid)
                                                                 .execute
                                                                 .first
@@ -91,6 +93,10 @@ module Mutations
           user_array.map.with_index { |param, i| param.to_h.merge(user: matched_users[i]) }
         end
 
+        def raise_project_not_found
+          raise Gitlab::Graphql::Errors::ArgumentError, 'The project could not be found'
+        end
+
         def raise_schedule_not_found
           raise Gitlab::Graphql::Errors::ArgumentError, 'The schedule could not be found'
         end

ee/spec/graphql/mutations/incident_management/oncall_rotation/create_spec.rb

@@ -90,6 +90,16 @@ RSpec.describe Mutations::IncidentManagement::OncallRotation::Create do
           end
         end
 
+        context 'project path incorrect' do
+          before do
+            args[:project_path] = "something/incorrect"
+          end
+
+          it 'raises an error' do
+            expect { resolve }.to raise_error(Gitlab::Graphql::Errors::ArgumentError, 'The project could not be found')
+          end
+        end
+
         context 'duplicate participants' do
           before do
             args[:participants] << args[:participants].first