make lastsync pref an int; don't set it in sync.js

services/sync/modules/wrap.js

@@ -165,6 +165,7 @@ let Wrap = {
 
       } catch (e) {
 	this._log.debug("Caught exception: " + Utils.exceptionStr(e));
+	this._log.debug("\n" + Utils.stackTrace(e));
       }
       self.done(ret);
     };

services/sync/services-sync.js

@@ -3,7 +3,7 @@ pref("extensions.weave.serverURL", "https://services.mozilla.com/");
 pref("extensions.weave.encryption", "aes-256-cbc");
 
 pref("extensions.weave.lastversion", "firstrun");
-pref("extensions.weave.lastsync", "0");
+pref("extensions.weave.lastsync", 0);
 
 pref("extensions.weave.ui.syncnow", true);
 pref("extensions.weave.ui.sharebookmarks", false);