determine last relevant keyword without considering ifnull() in the on clause

[k-sibyl]

When i handled sql like below, 'b.col1' is recognized as a table name in Parser.tables：
sql:"from table1 a left join table2 b on ifnull(a.col1, '') = ifnull(b.col1, '')"
When I commented out the lines 989 and 990 of code in the picture, the above-mentioned problem was solved.：