FindGlobalBMatrix should throw warning if no peaks indexed in a run

[RichardWaiteSTFC]

Describe the bug FindGlobalBMatrix will not warn the user if peaks in one of the runs cannot be indexed - it just spits out a poor UB for that run

To Reproduce To-Do

Expected behavior Would throw a warning and possibly not overwrite the UB on the workspace if it had one.

Screenshots

Platform/Version (please complete the following information):

• OS: [e.g. Windows, RHEL 7, Ubuntu, macOS]
• OS Version:
• Mantid Version [e.g. 6.0.0]

Additional context