actually fix decoding errors bugs

lib/routing.js

@@ -80,6 +80,7 @@ export const getQueryStringState = query => {
   }
 
   const state = mapper.map(mappings, query)
+  deserializeCode(state)
 
   Object.keys(state).forEach(key => {
     if (state[key] === '') state[key] = undefined
@@ -91,10 +92,27 @@ export const getQueryStringState = query => {
 export const updateQueryString = state => {
   if (history.location.search.indexOf('react_perf') < 0) {
     const mappedState = mapper.map(reverseMappings, state)
+    serializeCode(mappedState)
 
     history.replace({
-      // Do NOT change this to encodeURIComponent
       search: encodeURI(keysToQuery(mappedState))
     })
   }
 }
+
+// private
+function serializeCode(state) {
+  try {
+    if (state.code) state.code = encodeURIComponent(state.code)
+  } catch (e) {
+    // encoding errors should not crash the app
+  }
+}
+
+function deserializeCode(state) {
+  try {
+    if (state.code) state.code = decodeURIComponent(state.code)
+  } catch (e) {
+    // decoding errors should not crash the app
+  }
+}