fix(ImagePicker): 修复组件样式问题

由于 GridItem 组件样式修改导致组件样式出错

close #1085

Author: murongg

src/image-picker/index.less

@@ -51,4 +51,8 @@
   flex-direction: row;
   align-items: center;
   justify-content: center;
+}
+
+.l-grid-item {
+  padding: 0 !important;
 }

src/image-picker/index.wxml

@@ -1,6 +1,6 @@
 <!-- image-picker.wxml -->
 <l-grid row-num="{{ size }}" l-class="l-class">
-  <l-grid-item wx:for="{{ urls }}" wx:key="index" key="{{ index }}" slot="{{ index }}">
+  <l-grid-item wx:for="{{ urls }}" wx:key="index" key="{{ index }}" slot="{{ index }}" l-grid-item="l-grid-item">
     <view class="item l-item-class" catchtap="onPreviewTap" data-index="{{ index }}">
       <view class="close" data-index="{{ index }}" catchtap="onDelTap">
         <l-icon name="close" color="#fff" size="22" l-class="close-icon" />
@@ -9,7 +9,7 @@
     </view>
   </l-grid-item>
   <!-- add 按钮 -->
-  <l-grid-item wx:if="{{ showBtn }}">
+  <l-grid-item wx:if="{{ showBtn }}" l-grid-item="l-grid-item">
     <!-- 自定义图片选择按钮 -->
     <view class="item l-item-class {{size === 3? 'img': 'min-img'}}" catchtap="onAddTap" wx:if="{{ custom }}">
       <slot></slot>