Add better error messages for device and organize

Fixes #1364

src/device/mtploader.cpp

@@ -68,11 +68,16 @@ bool MtpLoader::TryLoad() {
 
   connection_ = make_unique<MtpConnection>(url_);
 
-  if (!connection_ || !connection_->is_valid()) {
+  if (!connection_) {
     emit Error(tr("Error connecting MTP device %1").arg(url_.toString()));
     return false;
   }
 
+  if (!connection_->is_valid()) {
+    emit Error(tr("Error connecting MTP device %1: %2").arg(url_.toString(), connection_->error_text()));
+    return false;
+  }
+
   // Load the list of songs on the device
   SongList songs;
   LIBMTP_track_t *tracks = LIBMTP_Get_Tracklisting_With_Callback(connection_->device(), nullptr, nullptr);