[BUG][FIX] TimeProfileBrowser ( [er][sm][et] looks OK, additional update provided )

[lewis at mail.msen.com]

I think that the "workaround" is OK. It is consistent with other error
handling appearing in the same method, and it produces the intended
result in the TimeProfileBrowser display (i.e. no bottom pane display
when lines in the GC listing are selected).

I am attaching (hopefully, BFAV willing) an updated version of Robert
Hirschfeld's change set with a more concise error check.
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