Fix a KeyError in GitlabSchema

app/graphql/gitlab_schema.rb

@@ -31,7 +31,7 @@ class GitlabSchema < GraphQL::Schema
   end
 
   def self.max_query_complexity(ctx)
-    current_user = ctx&.fetch(:current_user)
+    current_user = ctx&.fetch(:current_user, nil)
 
     if current_user&.admin
       ADMIN_COMPLEXITY

spec/graphql/gitlab_schema_spec.rb

@@ -34,12 +34,22 @@ describe GitlabSchema do
   end
 
   context 'for different types of users' do
-    it 'returns DEFAULT_MAX_COMPLEXITY for no user' do
-      expect(GraphQL::Schema).to receive(:execute).with('query', hash_including(max_complexity: GitlabSchema::DEFAULT_MAX_COMPLEXITY))
+    it 'returns DEFAULT_MAX_COMPLEXITY for no context' do
+      expect(GraphQL::Schema)
+        .to receive(:execute)
+        .with('query', hash_including(max_complexity: GitlabSchema::DEFAULT_MAX_COMPLEXITY))
 
       described_class.execute('query')
     end
 
+    it 'returns DEFAULT_MAX_COMPLEXITY for no user' do
+      expect(GraphQL::Schema)
+        .to receive(:execute)
+        .with('query', hash_including(max_complexity: GitlabSchema::DEFAULT_MAX_COMPLEXITY))
+
+      described_class.execute('query', context: {})
+    end
+
     it 'returns AUTHENTICATED_COMPLEXITY for a logged in user' do
       user = build :user