fix(rn): image in form bug (#11459)

Author: zhiqingchen

packages/taro-components-rn/src/components/Form/index.tsx

@@ -56,7 +56,7 @@ class _Form extends React.Component<FormProps> {
   }
 
   deppDiveIntoChildren = (children: React.ReactNode): React.ReactNode => {
-    return React.Children.toArray(children).map((child: any) => {
+    const result = React.Children.toArray(children).map((child: any) => {
       const childTypeName = child.type && child.type.name
       if (!child.type) return child
       if (childTypeName === '_Button' && ['submit', 'reset'].indexOf(child.props.formType) >= 0) {
@@ -74,6 +74,7 @@ class _Form extends React.Component<FormProps> {
         ? this.bindValueChangeEvent(child)
         : React.cloneElement(child, { ...child.props }, this.deppDiveIntoChildren(child.props.children))
     })
+    return result.length ? result : null
   }
 
   submit = (): void => {