review fixes

packages/share/android/src/main/java/io/flutter/plugins/share/SharePlugin.java

@@ -43,8 +43,7 @@ public void onAttachedToActivity(ActivityPluginBinding binding) {
 
   @Override
   public void onDetachedFromActivity() {
-    share.setActivity(null);
-    methodChannel.setMethodCallHandler(null);
+    tearDownChannel();
   }
 
   @Override
@@ -63,4 +62,9 @@ private void setUpChannel(BinaryMessenger messenger) {
     handler = new MethodCallHandler(share);
     methodChannel.setMethodCallHandler(handler);
   }
+
+  private void tearDownChannel() {
+    share.setActivity(null);
+    methodChannel.setMethodCallHandler(null);
+  }
 }