image/loading: Display first error, ignore second

Usually the first error is the relevant one. So show this one.

Why we get more than one error at all is a bit unclear.

src/decoder/formats/svg.rs

@@ -69,6 +69,7 @@ impl Svg {
         let (wakeup, wakeup_resv) = mpsc::unbounded();
 
         updater.clone().spawn_error_handled(async move {
+            log::trace!("Setting up SVG loader");
             let mut loader = glycin::Loader::new(file);
 
             #[cfg(feature = "disable-glycin-sandbox")]

src/widgets/image/loading.rs

@@ -220,6 +220,12 @@ impl imp::LpImage {
 
     fn set_error(&self, err: Option<anyhow::Error>) {
         log::debug!("Decoding error: {err:?}");
+
+        // Keeping first error instead of replacing with new error
+        if err.is_some() && self.error.borrow().is_some() {
+            return;
+        }
+
         self.error.replace(err.as_ref().map(|x| x.to_string()));
         self.obj().notify_error();