Always add an error handler

Otherwise Maplibre logs every error, including AbortError, which is
unhelpful. Our new default error handler calls the event handler if
present, and if not, it also logs errors, except for AbortError.

Author: dimfeld

src/lib/MapLibre.svelte

@@ -17,6 +17,7 @@
   import FullscreenControl from './FullscreenControl.svelte';
   import ScaleControl from './ScaleControl.svelte';
   import type { Snippet } from 'svelte';
+  import { handlers } from 'svelte/legacy';
 
   interface Props {
     map?: maplibregl.Map;
@@ -223,6 +224,17 @@
   let sourcesToReAddAfterStyleChange: Record<string, SourceSpecification> | undefined =
     $state(undefined);
 
+  function handleError(event: ErrorEvent) {
+    if (onerror) {
+      onerror(event);
+    } else if (event.error.name !== 'AbortError') {
+      // If there's no error handler, just log it to match the default behavior from MapLibre.
+      // But skip AbortError since that's a normal thing that happens inside certain sources,
+      // and not useful to log.
+      console.error(event);
+    }
+  }
+
   function createMap(element: HTMLDivElement) {
     onHashChange();
 
@@ -265,9 +277,7 @@
       loaded = true;
     });
 
-    if (onerror) {
-      map.on('error', onerror);
-    }
+    map.on('error', handleError);
 
     if (onmovestart) {
       map.on('movestart', onmovestart);