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Threre is a problem in display of "Sources and Forms Window".

When multiple translation(*.ts) files are loaded simultaneously, one ts file's "Sources and Forms Window" displays "Source code not available".
Open the file which is not related to this each other to reproduce this.

The reproduction procedure are as follows.

[Reproduction Procedure]
1) Execute Qt Linguist.
2) Select [Menu->File->Open...]
3) Select $QTDIR/translations/assistant_ja.ts
4) Select [Menu->File->Open...]
5) Change "Files of type:" ComboBox to "Translation files".
6) Select $QTDIR/translations/designer_ja.ts
7) Select "No" Button in dialog as follows.
「The file 'path/to/designer_ja.ts'does not seem to be related to the currentlyo pen file(s)
'path/to/assistant_ja.ts' Close the open file(s) first?」
8) Select "AbstractFindWidget" in Context Window.
9) "Source And Forms Window" display "Source code not available".
If you click "Japnese translation", and then "Source And Forms Window" become available