TextBox throws NullPointerException in the following scenario: I create a new .ppt file using PowerPoint, with an empty textbox in it (that says: "click to add text"), and than create an instance of Slide, and call the getShapes() method (some of the shapes are TextBox instances). This causes the TextBox class to throw NullPointerExceptions, in methods getText(), setSheet(), because the mebmer _txtrun is null.
Created attachment 18597 [details] an example of an "empty" TextBox
I've added a fix, so you'll no longer get an NPE However, until we add code to add in the text related record that your TextBox is missing, the TextBox is going to be fairly useless.