"Delete and add to ignore list" does not work when more than 16 files are selected

What steps will reproduce the problem?

1. Commit 17 or more files.
2. Select these 17 or more files, then do "TortoiseGit" --> "Delete and add to ignore list" --> "Delete and ignore 16 items by name" (or by extension)
3. ... but nothing happens ("Ignore" window does not appear)

What is the expected output? What do you see instead?

The "Ignore" window is expected to select Ignore Type and Ignore File. It appears only when 16 or less files are selected.

What version of TortoiseGit and Git are you using? On what operating system?

Windows 7 Professional 64 bit Rus Service Pack 1 TortoiseGit 2.1.0.0 (C:\Program Files\TortoiseGit\bin) git version 2.5.1.windows.1 (C:\Program Files\Git\bin; C:\Program Files\Git\mingw64; C:\Program Files\Git\mingw64\etc\gitconfig; C:\ProgramData\Git\config)

Please provide any additional information below.