Don't undo a render process. Fixes #438
Undoing a render appears to stop it in the ROP parameters view (ie : the "Abort Render" button is replaced by the "Render" button) and "undoing" a render abort appears to restart it. This might be confusing.
Undoing a render appears to stop it in the ROP parameters view (ie : the "Abort Render" button is replaced by the "Render" button) and "undoing" a render abort appears to restart it. This might be confusing.