fixes

src/common/common.css

@@ -336,7 +336,7 @@ previous button's border...
 --------------------------------------------------------------------------------------------------*/
 
 .fc-divider {
-	border-color: inherit;
+	border-color: inherit; /* for Bootstrap theme. eventually use instead of hardcoded color above */
 	border-style: solid;
 	border-width: 1px;
 }

src/theme/Theme.js

@@ -57,7 +57,7 @@ var Theme = Class.extend({
 
 
 	getClass: function(key) {
-		return this.classes[key];
+		return this.classes[key] || '';
 	},
 
 
@@ -67,6 +67,8 @@ var Theme = Class.extend({
 		if (className) {
 			return this.baseIconClass + ' ' + className;
 		}
+
+		return '';
 	},
 
 
@@ -80,6 +82,8 @@ var Theme = Class.extend({
 				return this.applyIconOverridePrefix(className);
 			}
 		}
+
+		return '';
 	}
 
 });