Add check for blank param value using allow_blank

lib/api/error_tracking.rb

@@ -29,7 +29,7 @@ module API
         success Entities::ErrorTracking::ProjectSetting
       end
       params do
-        requires :active, type: Boolean, desc: 'Specifying whether to enable or disable error tracking settings'
+        requires :active, type: Boolean, desc: 'Specifying whether to enable or disable error tracking settings', allow_blank: false
       end
 
       patch ':id/error_tracking/settings/' do

spec/requests/api/error_tracking_spec.rb

@@ -55,6 +55,14 @@ describe API::ErrorTracking do
           expect(json_response['error'])
             .to eq('active is invalid')
         end
+
+        it 'returns 400 if active is empty' do
+          make_patch_request(active: '')
+
+          expect(response).to have_gitlab_http_status(:bad_request)
+          expect(json_response['error'])
+            .to eq('active is empty')
+        end
       end
 
       context 'without a project setting' do