CommandHistory: Set default for "extensions.ubiquity.history.bin". Prevented empty histories.

ubiquity/defaults/preferences/preferences.js

@@ -15,6 +15,7 @@ pref("extensions.ubiquity.bugReportUri",
      "https://ubiquity.mozilla.com/report-bug/new/");
 pref("extensions.ubiquity.commandList.sortMode", "feed");
 pref("extensions.ubiquity.collectUsageData", false);
+pref("extensions.ubiquity.history.bin", "?");
 pref("extensions.ubiquity.history.max", 42);
 pref("extensions.ubiquity.doNounFirstExternals", 0);
 pref("extensions.ubiquity.inputDelay", 50);

ubiquity/modules/cmdhistory.js

@@ -43,7 +43,8 @@ const SEPARATOR = "\n";
 
 var CommandHistory = this, cursor = -1, _bin = null;
 
-function get() _bin || (_bin = Utils.prefs.get(PREF_BIN).split(SEPARATOR));
+function get() _bin || (
+  _bin = Utils.prefs.get(PREF_BIN).split(SEPARATOR).filter(Boolean));
 function set(arr) {
   _bin = arr;
   return save();