Emulator

Game Name?
Any WiiWare WAD or Wii game in WBFS format

Game ID?
N/A

What's the problem? Describe what went wrong in few words.
If multiple games are selected at once, it is possible to have Dolphin compress a .WAD or .WBFS file in a .GCZ format. Compressed .wbfs files are recognised as invalid files, while running compressed .WAD files will cause Dolphin to crash.

What did you expect to happen instead?
It should not be possible to compress .wbfs or .wad files.

What steps will reproduce the problem?

1. Open Dolphin's game library
2. Select at least 2 games at once, one of which being a .wad or .wbfs
3. Right click the selected files and click "Compress selected ISOs..."

Dolphin 3.5 and 3.5-367 are old versions of Dolphin that have
known issues and bugs, so don't report issues about them and test the
latest Dolphin version first.
Which versions of Dolphin did you test on?
4.0-3413
3.0-479

Does using an older version of Dolphin solve your issue? If yes, which
versions of Dolphin used to work?
No

What are your PC specifications? (including, but not limited to: Operating
System, CPU and GPU)
Windows 8, 64 bit

Is there any other relevant information? (e.g. logs, screenshots,
configuration files)
N/A