Putting an Ender Dragon into a spawner summons a ghost dragon

When you place a n Ender Dragon into a spawner, a large unanimated dragon appears. There is still a dragon in the spawner itself, but the ghost will also disappear when the spawner is broken.

Steps to reproduce:

• Place a trial spawner or a regular spawner.
• give yourself an Ender Dragon spawn egg.
• Place the spawn egg into the spawner.

What should happen:
The ghost dragon should not show up.