Don't change state when distance hasn't changed

lib/store/reducer.js

@@ -154,19 +154,24 @@ function itemUpdated(state, id, { distance }) {
 
   if (!previous) return state;
 
-  const item = {
+  const next = {
     ...previous,
     value: {
       ...previous.value,
       ...normalizeDistance(distance, previous.value),
     },
   };
 
+  // right now the only item update possible is distance,
+  // if that hasn't changed, abort to prevent react rerendering
+  const distanceChanged = next.value.distance !== previous.value.distance;
+  if (!distanceChanged) return state;
+
   return {
     ...state,
     items: {
       ...items,
-      [id]: item,
+      [id]: next,
     },
   };
 }