fix(commune): no crash on blank codes

app/services/api_geo_service.rb

@@ -123,7 +123,7 @@ class APIGeoService
     end
 
     def safely_normalize_city_name(department_code, city_code, fallback)
-      return fallback if department_code.nil? || city_code.nil?
+      return fallback if department_code.blank? || city_code.blank?
 
       commune_name(department_code, city_code) || fallback
     end

spec/services/api_geo_service_spec.rb

@@ -130,5 +130,17 @@ describe APIGeoService do
 
       it { is_expected.to eq('Paris') }
     end
+
+    context 'with blank department' do
+      let(:department_code) { '' }
+
+      it { is_expected.to eq('Paris') }
+    end
+
+    context 'with blank city_code' do
+      let(:city_code) { '' }
+
+      it { is_expected.to eq('Paris') }
+    end
   end
 end