just hide toottip overlay when there is no title

avoid rerender children when title is changed

components/tooltip/index.jsx

@@ -10,6 +10,14 @@ export default React.createClass({
       mouseLeaveDelay: 0.1
     };
   },
+  getInitialState() {
+    return {
+      visible: false
+    };
+  },
+  onVisibleChange(visible) {
+    this.setState({ visible });
+  },
   render() {
     let transitionName = ({
       top: 'zoom-down',
@@ -17,12 +25,21 @@ export default React.createClass({
       left: 'zoom-right',
       right: 'zoom-left'
     })[this.props.placement];
+
+    // Hide tooltip when there is no title
+    let visible = this.state.visible;
+    if (!this.props.title) {
+      visible = false;
+    }
+
     return (
-      this.props.title ? <Tooltip transitionName={transitionName}
+       <Tooltip transitionName={transitionName}
         overlay={this.props.title}
+        visible={visible}
+        onVisibleChange={this.onVisibleChange}
         {...this.props}>
         {this.props.children}
-      </Tooltip> : this.props.children
+      </Tooltip>
     );
   }
 });

style/components/tooltip.less

@@ -52,6 +52,7 @@
   background-color: @tooltip-bg;
   border-radius: @border-radius-base;
   box-shadow: @overlay-shadow;
+  min-height: 34px;
 }
 
 // Arrows