Call map.panTo() only once on first hop

`map.panTo` was called twice on the first hop, once on [line 55](https://github.com/opendatacity/prism/blob/3b09fb00bdad4c1077616118699b4b64aa2d417a/assets/js/index.js#L55) and immediately after on [line 62](https://github.com/opendatacity/prism/blob/3b09fb00bdad4c1077616118699b4b64aa2d417a/assets/js/index.js#L62).

For me, this sometimes caused the initial map pan not to trigger at all, it would only start panning on the second hop then. Calling `map.panTo` only once seems to fix this behavior.