Only attempt to show receipts if there are any.

Previously "Receipts:" was still shown.

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required (VERSION 3.6)
 project (whyblocked
-         VERSION 0.6.1
+         VERSION 0.6.2
          LANGUAGES CXX
 )
 

src/interface_text.cpp

@@ -151,6 +151,8 @@ const bool whyblocked_text::start()
                         }
                         cout << std::get<1>(result) << '\n';
 
+                        if (!std::get<2>(result).empty())
+                        {
                             cout << "Receipts:\n";
                             for (const string &url : std::get<2>(result))
                             {
@@ -158,6 +160,7 @@ const bool whyblocked_text::start()
                             }
                         }
                     }
+                }
                 break;
             }
             case 'h':