DisplayBug:20101 VariantTitle exists without a parent title

Title 21782 is broken. It displays:

IndexError A problem occurred in a Python script. Here is the sequence of function calls leading up to the error, in the order they occurred. /www/isfdb.tamu.edu/root/cgi-bin/title.cgi 176        elif title[TITLE_PARENT]: 177                parent_title = SQLloadTitle(title[TITLE_PARENT]) 178                if parent_title[TITLE_SERIES]: 179                        series = SQLget1Series(parent_title[TITLE_SERIES]) 180                        print " " parent_title = [], TITLE_SERIES = 5 IndexError: list index out of range args = ('list index out of range',)

Above, it says Variant Title ERROR: Parent Title=152900. This title (152900) is nonexistent. I have no idea how it got this way.