fix(developer): handle crash reports without Keyman Engine installed

Fixes #7656.

If Keyman Developer is installed, but not Keyman for Windows, then
tsysinfo.exe is not present. If a crash occurs, this causes a secondary
crash when trying to display the error handler dialog. In this
situation, we now just show a dialog box with a short message rather
than the more friendly dialog available via tsysinfo.exe.

We could consider adding tsysinfo.exe into Keyman Developer for a future
release.