Revert "fix(ngOptions): skip comments when looking for option elements"

This reverts commit 7f3f3dd.
The fix only fixed a specific case and exhibited a flawed logic
(namely skipping every option if the emptyOption is a comment).
See #12190 (comment)

Conflicts:
	test/ng/directive/ngOptionsSpec.js

src/ng/directive/ngOptions.js

@@ -621,10 +621,7 @@ var ngOptionsDirective = ['$compile', '$parse', function($compile, $parse) {
         if (emptyOption_ || unknownOption_) {
           while (current &&
                 (current === emptyOption_ ||
-                current === unknownOption_ ||
-                emptyOption_ && emptyOption_.nodeType === NODE_TYPE_COMMENT)) {
-            // Empty options might have directives that transclude
-            // and insert comments (e.g. ngIf)
+                current === unknownOption_)) {
             current = current.nextSibling;
           }
         }

test/ng/directive/ngOptionsSpec.js

@@ -2144,30 +2144,6 @@ describe('ngOptions', function() {
     });
 
 
-    it('should be possible to use ngIf in the blank option', function() {
-      var option;
-      createSingleSelect('<option ng-if="isBlank" value="">blank</option>');
-
-      scope.$apply(function() {
-        scope.values = [{name: 'A'}];
-        scope.isBlank = true;
-      });
-
-      expect(element.find('option').length).toBe(2);
-      option = element.find('option').eq(0);
-      expect(option.val()).toBe('');
-      expect(option.text()).toBe('blank');
-
-      scope.$apply(function() {
-        scope.isBlank = false;
-      });
-
-      expect(element.find('option').length).toBe(1);
-      option = element.find('option').eq(0);
-      expect(option.text()).toBe('A');
-    });
-
-
     it('should not throw when a directive compiles the blank option before ngOptions is linked', function() {
       expect(function() {
         createSelect({