Cannot show compressed image of which topic is not advertised when selected

[furushchev]

When an image topic is selected and the topic is still not advertised by its publisher, rqt_image_view subscribes the topic as raw transport ( the type of message is sensor_msgs/Image).
If the topic is advertised as transport other than raw after the subscription, image of the topic never shows up due to message type mismatch ( sensor_msgs/CompressedImage != sensor_msgs/Image ).

To reproduce the issue:

1. Run image publisher ( i.e. it publishes publisher/image, publisher/image/compressed)

2. Run rqt_image_view and select publisher/image/compressed (Image shows up)

3. Kill image publisher, then press refresh button on rqt_image_view (it clear images and turns to grey screen)

4. Run image publisher again

5. Image never shows up
   (From the image publisher, the error message is displayed:

   Client [/rqt_gui_cpp_node_4001128] wants topic /publisher/image/compressed to have datatype/md5sum [sensor_msgs/Image/060021388200f6f0f447d0fcd9c64743], but our version has [sensor_msgs/CompressedImage/8f7a12909da2c9d3332d540a0977563f]. Dropping connection.