fix: avoid error when has no rate record

lib/rating/models/rating/rating.rb

@@ -101,7 +101,7 @@ module Rating
         count = distinct ? 'COUNT(DISTINCT resource_id)' : 'COUNT(1)'
 
         %((
-          SELECT #{count}
+          SELECT GREATEST(#{count}, 1)
           FROM #{rate_table_name}
           WHERE resource_type = :resource_type AND #{scope_type_query(scopeable)}
         ))

spec/models/rating/update_rating_spec.rb

@@ -4,9 +4,9 @@ require 'rails_helper'
 require 'support/shared_context/with_database_records'
 
 RSpec.describe Rating::Rating, ':update_rating' do
+  context 'with no scopeable' do
     include_context 'with_database_records'
 
-  context 'with no scopeable' do
     it 'updates the rating data of the given resource' do
       record = described_class.find_by(resource: article_1)
 
@@ -18,6 +18,8 @@ RSpec.describe Rating::Rating, ':update_rating' do
   end
 
   context 'with scopeable' do
+    include_context 'with_database_records'
+
     it 'updates the rating data of the given resource respecting the scope' do
       record = described_class.find_by(resource: article_1, scopeable: category)
 
@@ -27,4 +29,20 @@ RSpec.describe Rating::Rating, ':update_rating' do
       expect(record.total).to    eq 2
     end
   end
+
+  context 'when rate table has no record' do
+    let!(:resource) { create :article }
+    let!(:scope)    { nil }
+
+    it 'calculates with counts values as zero' do
+      described_class.update_rating resource, scope
+
+      record = described_class.last
+
+      expect(record.average).to  eq 0
+      expect(record.estimate).to eq 0
+      expect(record.sum).to      eq 0
+      expect(record.total).to    eq 0
+    end
+  end
 end