Get parent of undefined is it possible?

Question

My script is resizing object when the context is "Text" i.e. there is some insertion point. I use this code to get object to resize:
if (selection[0].constructor.name = "InsertionPoint")
objectToResize = selection[0].parentTextFrames[0];
It works good until cursor is visible. But when object becomes small enough cursor goes out of visible area and "selection[0]" is undefined. How can I get access to the object in this case?

Answer 1

Full source code:
with (app) {
for (i = 0; i < selection.length; i++) {
var objectToResize = selection[i];
switch (objectToResize.constructor.name) {
case "InsertionPoint": case "Character": case "Text": case "Word": case "Paragraph": case "TextColumn":
objectToResize = objectToResize.parentTextFrames[0];
var myBounds = objectToResize.geometricBounds;
delta = activeDocument.gridPreferences.horizontalGridlineDivision / activeDocument.gridPreferences.horizontalGridSubdivision;
myBounds[3] = myBounds[3] + delta;
objectToResize.geometricBounds = myBounds;
Error appears at line:
var myBounds = objectToResize.geometricBounds;