remove empty state values so as not to override defaults

lib/routing.js

@@ -44,7 +44,16 @@ const keysToQuery = keys =>
     .map(key => `${key}=${keys[key]}`)
     .join('&')}`
 
-export const getQueryStringState = query => mapper.map(mappings, query)
+export const getQueryStringState = query => {
+  const state = mapper.map(mappings, query)
+
+  Object.keys(state).forEach(key => {
+    if (state[key] === '') state[key] = undefined
+  })
+
+  return state
+}
+
 export const updateQueryString = state =>
   history.replace({
     search: encodeURI(keysToQuery(mapper.map(reverseMappings, state)))