[CS3 JS] Finding paragraph containing table

Question

I have a table object and want to find the paragraph that contains the table. Then I want to return the contents of the paragraph previous to the table anchor. I am using this, but when I attempt to display the contents of the paragraph, I get "Object is invalid". Thanks for any help you can provide.
// Get the paragraph inside the table.
var oPgf = app.selection[0].paragraphs[0];
// Make sure the paragraph is in a cell.
if (oPgf.parent.constructor.name === "Cell") {
  // Get the parent cell and table objects.
  var oCell = oPgf.parent;
  var oTbl = oCell.parent;
  // Get the paragraph containing the table.
  var oPgf2 = oTbl.storyOffset.paragraphs[0];
  // Get the story object of the paragraph.
  var oStory = oPgf.parentStory;
  // Get the paragraph's index.
  var iPos = oPgf2.index;
  // Display the contents of the paragraph before the table anchor.
  alert (oStory.paragraphs[iPos-1].contents);
Rick Quatro
585-659-8267

Answer 1

I found a previous post that is helping me with this.
// Paragraph inside of table.
var oPgf = app.selection[0].paragraphs[0];
// Make sure the paragraph is inside a table
if (oPgf.parent.constructor.name === "Cell") {
  var oCell = oPgf.parent;
  var oTbl = oCell.parent;
  // Get the paragraph containing the table anchor.
  var oPgf2 = oTbl.storyOffset.paragraphs[0];
  // Loop from the table anchor to the top of the story.
  while (oPgf2) {
    $.writeln(oPgf2.constructor.name);
    oPgf2 = oPgf2.parentStory.paragraphs.previousItem(oPgf2);
This basically works, except this line gives an "Object is invalid" error when it gets to the beginning of the story:
oPgf2 = oPgf2.parentStory.paragraphs.previousItem(oPgf2);
I can use a try statement, but I am wondering why the loop doesn't exit gracefully without an error. Thanks.
Rick