@param lineIndex index of line
@return the logical starting offset of the line. When there are not any lines,
getOffsetAtLine(0) is a valid call that should answer 0.
@exception IllegalArgumentException <ul>
<li>ERROR_INVALID_ARGUMENT when lineIndex is out of range</li>
</ul>
Returns the logical offset of the given line. <p>
@param lineIndex index of line @return the logical starting offset of the line. When there are not any lines, getOffsetAtLine(0) is a valid call that should answer 0. @exception IllegalArgumentException <ul> <li>ERROR_INVALID_ARGUMENT when lineIndex is out of range</li> </ul>