docs: fix js error when there's no api level cookie saved.

currently, if there's no api level cookie saved, then
the selectedLevelItem variable will be undefined and will
throw an error at the end of the buildApilevelSelector function.
Now, userApiLevel is set to the max level in this case.

tools/droiddoc/templates/assets/android-developer-reference.js

@@ -26,6 +26,7 @@ function buildApiLevelSelector() {
   var maxLevel = SINCE_DATA.length;
   var userApiLevelEnabled = readCookie(API_LEVEL_ENABLED_COOKIE);
   var userApiLevel = readCookie(API_LEVEL_COOKIE);
+  userApiLevel = userApiLevel == 0 ? maxLevel : userApiLevel; // If there's no cookie (zero), use the max by default
 
   if (userApiLevelEnabled == 0) {
     $("#apiLevelSelector").attr("disabled","disabled");