Fix item cache being deleted on fetch.

src/store/reducers.ts

@@ -155,8 +155,10 @@ export const items = handleActions(
     },
     [actions.setCacheCollection.toString()]: (state: CacheItemsData, action: ActionMeta<CacheCollection, { colUid: string }>) => {
       if (action.payload !== undefined) {
+        if (!state.has(action.meta.colUid)) {
           return state.set(action.meta.colUid, ImmutableMap());
         }
+      }
       return state;
     },
     [actions.unsetCacheCollection.toString()]: (state: CacheItemsData, action: ActionMeta<string, { colUid: string }>) => {