This happened when one of our modules had clipboard content and was
closed, which currently clears the clipboard, and then reopened and
attempting to paste the content. Apparently the utf-16 mime-type is
still alive but the content isn't, on which rtl_str_getLength(pText)
asserts.

Change-Id: I5cc7c20ac1f1a8551a10b033e1f37bf83c5cc202