fix issue #144 if/else if/else expression with trailing blanks does not evaluate properly

[vboulaye]

A few years later, I just stumbled across the same error.
But this time I think I know how to fix it!

While debugging I found out that the problem disappear on the second compilation of the same expression.
And I saw that the end property is not updated properly when setting the expression as a String and removing trailing blanks in AbstractParser.setExpression(String expression)

So here is my attempt to fix this issue.

[ScottCUSA]

This might also fix #342 or at least the issues may be related.