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.