Switching from shared web workers (not supported by chrome on android) to "normal" web workers.

src/components/map/Gpxes.tsx

@@ -23,7 +23,9 @@ export const Gpxes: react.FC<GpxesProperties> = (props: GpxesProperties) => {
       console.log(`Gpxes, visibles: ${JSON.stringify(gpxes)}`);
       setVisibleGpxes(gpxes);
     };
-    getVisibleGpxes();
+    if (props.viewPort !== undefined) {
+      getVisibleGpxes();
+    }
   }, [
     props.viewPort?.bottomRight.x,
     props.viewPort?.bottomRight.y,