ExtendScript doesn't work consistently

The message in ExtendScript is "undefined is not an object" and it locks up FM.

Bold is a character format that does exist in the document.

The script goes through my document, looks for specific paragraph styles, and then bolds certain words in the paragraph. (I was able to put it together using pieces of other scripts that I had lots of help from from you folks in the forum. 🙂 ) The red text below is where it breaks down.  Like I said, it works in all the documents except one, so I figure it must be something in the document.

#target framemaker
main ();

// Check for an open document
function main () {
var doc;

doc = app.ActiveDoc;
if (doc.ObjectValid () === 1) {
processDoc (doc);
}
else {
alert ("There is no active document.");
}
}

function processDoc (doc) {
var pgfRegex, pgf;

// Turn off the displaying property to speed the script and prevent flicker.
if (app.Displaying === 1) {
app.Displaying = 0;
}
pgf = doc.FirstPgfInDoc;
// Match CaptionFigure and CaptionTable paragraph formats.
pgfRegex = /^(CaptionFigure|CaptionTable|CaptionPlate)$/;

while (pgf.ObjectValid () === 1) {
if (pgfRegex.test (pgf.Name) === true) {
boldTheText (pgf, doc);
}
pgf = pgf.NextPgfInDoc;
}

// Restore the document's display and refresh the screen.
if (app.Displaying === 0) {
app.Displaying = 1;
doc.Redisplay ();
alert("Text is bolded");
}
}
function boldTheText (pgf, doc) {

var end = Constants.FV_OBJ_END_OFFSET - 1, begin = 0, textRange, charTag;

var textList = pgf.GetText (Constants.FTI_String);
for (var i = textList.length - 1; i >= 0; i -= 1)
{
num = getFigOrTable (pgf);
begin = num.index;
end = begin + num[0].length;

textRange = new TextRange (new TextLoc (pgf, begin), new TextLoc (pgf, end));
applyCharFmt (textRange, "Bold", doc);
}

}

function getFigOrTable (pgf) {

var doc;

doc = app.ActiveDoc;

var regex, pgfText, match;

regex = /(?:Figure|Table|Plate) ((AF|AT|[FTP])(\d+)([.]| [(]continued[)][.]))/; // Match figure or table and number in text.

pgfText = getText (pgf, doc);

if (regex.test (pgfText) === true) {

match = pgfText.match (regex);

return (match);

}

}

function getText (textObj, doc) {

// Gets the text from the text object or text range.

var text = "", textItems, i;

// Get a list of the strings in the text object or text range.

if (textObj.constructor.name !== "TextRange") {

textItems = textObj.GetText(Constants.FTI_String);

} else {

textItems = doc.GetTextForRange(textObj, Constants.FTI_String);

}

// Concatenate the strings.

for (i = 0; i < textItems.len; i += 1) {

text += (textItems[i].sdata);

}

return text; // Return the text

}

function applyCharFmt (textRange, name, doc) {

var charFmt = 0;

charFmt = doc.GetNamedCharFmt (name);

if (charFmt.ObjectValid()) {

doc.SetTextProps (textRange, charFmt.GetProps());

}

}

As Bob said, we will definitely need more details about the script what it is supposed to do.

The forum has a number of scripters [and I'm not one]. Several are professional. They run into odd issues [some real bugs], but I'm going to guess that they'll need more info to be of help, starting with:
• what is the function of the script?
• what is the failure mode?