Fix a bug where you can't save empty fields if there's a non-empty default. Also made the option saving code more robust to similar scenarios

Author: ilya

options.html

@@ -80,7 +80,9 @@
   var defaultSettings = chrome.extension.getBackgroundPage().defaultSettings;
 
   var editableFields = ["scrollStepSize", "defaultZoomLevel", "excludedUrls", "linkHintCharacters",
-    "userDefinedLinkHintCss", "keyMappings"];
+                        "userDefinedLinkHintCss", "keyMappings"];
+
+  var canBeEmptyFields = ["excludedUrls", "keyMappings", "userDefinedLinkHintCss"];
 
   var postSaveHooks = {
     keyMappings: function (value) {
@@ -118,10 +120,17 @@
       var fieldValue = $(fieldName).value.trim();
       var defaultFieldValue = (defaultSettings[fieldName] != null) ?
         defaultSettings[fieldName].toString() : "";
+
+      // Don't save to storage if it's equal to the default
       if (fieldValue == defaultFieldValue)
         delete localStorage[fieldName];
-      else
+      // ..or if it's empty and not a field that we allow to be empty.
+      else if (!fieldValue && canBeEmptyFields.indexOf(fieldName) == -1) {
+        delete localStorage[fieldName];
+        fieldValue = defaultFieldValue;
+      } else
         localStorage[fieldName] = fieldValue;
+
       $(fieldName).value = fieldValue;
       $(fieldName).setAttribute("savedValue", fieldValue);
 
@@ -133,7 +142,12 @@
   // Restores select box state to saved value from localStorage.
   function populateOptions() {
     for (var i = 0; i < editableFields.length; i++) {
-      $(editableFields[i]).value = localStorage[editableFields[i]] || defaultSettings[editableFields[i]] || "";
+      // If it's null or undefined, let's go to the default. We want to allow empty strings in certain cases.
+      if (localStorage[editableFields[i]] != "" && !localStorage[editableFields[i]]) {
+        $(editableFields[i]).value = defaultSettings[editableFields[i]] || "";
+      } else {
+        $(editableFields[i]).value = localStorage[editableFields[i]];
+      }
       $(editableFields[i]).setAttribute("savedValue", $(editableFields[i]).value);
     }
   }