优化icon属性设置

src/form/select.wc

@@ -268,7 +268,6 @@ export default class Select {
     this.__OUTER__ = this.root.children[1]
     this.__PREPEND__ = this.__OUTER__.children[0]
     this.__INPUT__ = this.__OUTER__.children[1]
-    this.__ICO__ = this.__OUTER__.children[2]
     this.__APPEND__ = this.__OUTER__.children[3]
     this.__OPTG__ = this.__OUTER__.children[4]
   }

src/icon/index.wc

@@ -121,21 +121,13 @@ export default class Icon {
     }
   }
 
-  get is() {
-    return this.props.is
-  }
-
-  set is(val) {
-    this.props.is = val
-    this.setAttribute('is', val)
-    this.drawPath()
-  }
-
   watch() {
     switch (name) {
       case 'is':
-        this.is = val
+        if (val) {
-        if (!val) {
+          this.props.is = val
+          this.drawPath()
+        } else {
           this.removeAttribute('is')
         }
         break

src/layer/index.wc

@@ -339,7 +339,7 @@ class Layer {
       case 'frame':
         if (val === 'notify') {
           var _ico = document.createElement('wc-icon')
-          _ico.is = 'close'
+          _ico.setAttribute('is', 'close')
           this.__TITLE__.appendChild(_ico)
         }
         btns = []