Keep compatibility with qBittorrent < 2.3.0 (import settings from the registry)

src/qinisettings.h

@@ -59,6 +59,15 @@ public:
           }
         }
       }
+    } else {
+      // Keep compatibility with qBittorrent < 2.3.0
+      // Import the setting from the registry
+      QSettings old_settings(organizationName(), applicationName());
+      ret = old_settings.value(key);
+      if(!ret.isEmpty()) {
+        setValue(key, ret);
+        old_settings.remove(key);
+      }
     }
     if(ret.isNull())
       return defaultValue;