A user reported in his blog that he had problems with JMC. This bug is one of the issues he describes. For the full text, see http://www.bannkreis.de/blog/home/bannkreisde/archives/2015-09/about_java_mission_control.int.html.
This happened to me after I unchecked the checkbox "Show dialog on alerts" on that very dialog. After that the dialog would reappear in random situations, sometimes every 5 seconds, without any alert in the list.
(I could do a cheap joke on this that I misinterpreted the meaning of the checkbox, with it being off actually meaning that the dialog would also show without alerts....but no I really want to be constructive here