fix(ngStyle): correctly remove old style when new style value is invalid

src/ng/directive/ngStyle.js

@@ -54,14 +54,7 @@
 var ngStyleDirective = ngDirective(function(scope, element, attr) {
   scope.$watchCollection(attr.ngStyle, function ngStyleWatchAction(newStyles, oldStyles) {
     if (oldStyles && (newStyles !== oldStyles)) {
-      if (!newStyles) {
-        newStyles = {};
-      }
-      forEach(oldStyles, function(val, style) {
-        if (newStyles[style] == null) {
-          newStyles[style] = '';
-        }
-      });
+      forEach(oldStyles, function(val, style) { element.css(style, ''); });
     }
     if (newStyles) element.css(newStyles);
   });

test/ng/directive/ngStyleSpec.js

@@ -143,6 +143,17 @@ describe('ngStyle', function() {
       expect(element.css(postCompStyle)).not.toBe('99px');
     });
 
+    it('should clear style when the value is false', function() {
+      scope.styleObj = {'height': '99px', 'width': '88px'};
+      scope.$apply();
+      expect(element.css(preCompStyle)).toBe('88px');
+      expect(element.css(postCompStyle)).toBe('99px');
+      scope.styleObj = {'height': false, 'width': false};
+      scope.$apply();
+      expect(element.css(preCompStyle)).not.toBe('88px');
+      expect(element.css(postCompStyle)).not.toBe('99px');
+    });
+
     it('should set style when the value is zero', function() {
       scope.styleObj = {'height': '99px', 'width': '88px'};
       scope.$apply();