fix(select): select option with a label of 0 is not shown

Bug caused by the use of the `||` operator to replace all non-truthy
values with an empty string. Changed to replace only `undefined` values.

Closes #1401

1 files changed, 5 insertions, 2 deletions

diff --git a/src/ng/directive/select.js b/src/ng/directive/select.js
index 0c94ddcb..e6e0ced7 100644
--- a/src/ng/directive/select.js
+++ b/src/ng/directive/select.js
@@ -386,7 +386,8 @@ var selectDirective = ['$compile', '$parse', function($compile,   $parse) {
               selected,
               selectedSet = false, // nothing is selected yet
               lastElement,
-              element;
+              element,
+              label;
 
           if (multiple) {
             selectedSet = new HashMap(modelValue);
@@ -410,9 +411,11 @@ var selectDirective = ['$compile', '$parse', function($compile,   $parse) {
               selected = modelValue === valueFn(scope, locals);
               selectedSet = selectedSet || selected; // see if at least one item is selected
             }
+            label = displayFn(scope, locals); // what will be seen by the user
+            label = label === undefined ? '' : label; // doing displayFn(scope, locals) || '' overwrites zero values
             optionGroup.push({
               id: keyName ? keys[index] : index,   // either the index into array or key from object
-              label: displayFn(scope, locals) || '', // what will be seen by the user
+              label: label,
               selected: selected                   // determine if we should be selected
             });
           }