This bug was separated from 4686956.

Under SPARC/Intel j2se JDK1.3.1_02, ja locale, JTextField causes
IllegalArgumentExceptionby when user pastes a text with mouse middles button
if there is a preedit string of converison. Implicit commit should be
functioned.


This bug is also seen with JDK1.3.1_02, JDK1.4.1 and JDK1.4.2 PIT build.

To reproduce:
     1) % java Sample attahced in 4686956.
     2) Conversion-on for Japanese input
     3) input something such as 'aiueo' and does not commit the string
     4) Paste some text into the JTextFiled by using mouse middle button
        *When paste the string, push mouse middle button on the preedit string
        of conversion. e.g.) put string on to 'aiueo' that still did not commit
        the string.
        -> It makes IllegalArgumentException.