title: get last non-blank row of column google sheets
body: <p>I need to go to the last non-blank cell in a column.
  For a long while, I've been using this code quite happily:</p>
  
  <pre><code>ss.getRange('A500').activate();
  ss.getCurrentCell().getNextDataCell(SpreadsheetApp.Direction.UP).activate();
  </code></pre>
  
  <p>but now it crashes saying: "We're sorry, a server error occurred. Please wait a bit and try again."
  Days later I still get the same message!</p>
  
  <p>When I debug, it won't go past the 2nd line above, so I guess that's where the problem is.</p>
  
  <p>I've searched for a solution, but can only find code that relies on no gaps in the column. My column has many blank cells above the last cell with data in it.</p>
  
  <p>Please help.</p>