Minor change manager bug

[Mark S. Miller <mark>]

I did a "history" from the menu in the classes pane of the System
Browser on the class BrowserView for which I had filed in some
changes.  It blew up when ChangeRecorder>>follow:from:backTo: did a 

	record <- self get: position

with a position of -1.  Dean tells me the position is -1 because this
class (BrowserView) precedes our logging.  Btw, I can do "history"
perfectly fine from the protocol & method panes.