[wp-trac] [WordPress Trac] #59553: In Beta 6.4-beta2, when trying to add a row or container, I get the error

[WordPress Trac]

#59553: In Beta 6.4-beta2, when trying to add a row or container, I get the error
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 Reporter:  texasfixer    |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  General       |    Version:  trunk
 Severity:  critical      |   Keywords:
  Focuses:                |
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Ticket URL: <https://core.trac.wordpress.org/ticket/59553>
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