Had this error appear twice today when typing in the search box and then hitting backspace until the search box is empty and then pressing backspace again. Can't seem to replicate it again now but it crashed MM twice for me today.
Just happened again. Also I don't really understand what's supposed to happen when backspacing all the way back until you've got an empty search box. If I then press backspace again it seems to cycle through different nodes. (e.g. I start off in the Music node and then keep pressing backspace in the search box until it's empty. At that point when it's deleted all characters and I press backspace again the view then jumps to display random nodes.)