IOS/KD: Disable download and mail when files are invalid

[noahpistilli]

As pointed out by @AdmiralCurtiss in #12184, when the WC24SendList::ReadSendList and/or NWC24Dl::ReadDlList fail, their class member m_data is being used by IOS when called.

This PR fixes it by exiting any function which calls an m_data member which failed to initialize. It also deletes the corrupted file, where either Dolphin or the Wii Menu will regenerate it for later use.

[AdmiralCurtiss]

Yes, that's a definite improvement. Can you also add a bunch of ASSERT(!IsDisabled()) at the start of every function that attempts to read from or write to m_data?