Check if BatchLoader is nil

- Fix MergeRequestsResolver to check BatchLoader
If project was not found BatchLoader object
can be nil and project.present? would still
return true

- Add specs for cases when Project is not resolved

app/graphql/resolvers/merge_requests_resolver.rb

@@ -15,7 +15,8 @@ module Resolvers
     alias_method :project, :object
 
     def resolve(**args)
-      return unless project.present?
+      project = object.respond_to?(:sync) ? object.sync : object
+      return MergeRequest.none if project.nil?
 
       args[:iids] ||= [args[:iid]].compact
 

spec/graphql/mutations/concerns/mutations/resolves_issuable_spec.rb

@@ -59,6 +59,12 @@ describe Mutations::ResolvesIssuable do
 
         expect(result).to be_nil
       end
+
+      it 'returns nil if parent path is empty' do
+        result = mutation.resolve_issuable(type: type, parent_path: "", iid: issuable.iid)
+
+        expect(result).to be_nil
+      end
     end
   end
 

spec/graphql/resolvers/merge_requests_resolver_spec.rb

@@ -52,6 +52,12 @@ describe Resolvers::MergeRequestsResolver do
 
       expect(result).to be_empty
     end
+
+    it 'resolves an unknown project to be empty' do
+      result = batch_sync { resolve_mr(nil, iid: iid_1) }
+
+      expect(result.compact).to be_empty
+    end
   end
 
   def resolve_mr(project, args)