[BUG] NPE in TableNamesFinder in AnalyticExpression visitor

[davyboyhayes]

SELECT c, SUM(COUNT(*)) OVER (ORDER BY c ASC ROWS UNBOUNDED PRECEDING) FROM tbl GROUP BY c

The window element here does not contain a range or an offset, yet this will throw an NPE in TableNamesFinder when it tries to walk the AnalyticExpression:

        String sqlStr = "SELECT c, SUM(COUNT(*)) OVER (ORDER BY c ASC ROWS UNBOUNDED PRECEDING) FROM tbl GROUP BY c";

        assertThatCode(() -> TablesNamesFinder.findTables(sqlStr))
                .doesNotThrowAnyException();

Gives:

Expecting code not to raise a throwable but caught                                                                                                                                                                                                                                                                                                                                                                                          
  "java.lang.NullPointerException: Cannot invoke "net.sf.jsqlparser.expression.WindowRange.getStart()" because the return value of "net.sf.jsqlparser.expression.WindowElement.getRange()" is null