Prevent stack trace calculation from being halted if any of the frames throws an error

[elliette]

Encountered this issue while debugging a google3 app.

When an app is paused at a breakpoint, DWDS attempts to get information about all the frames in the stack trace. If any part of that fails (for example, an error is thrown when DWDS tries to get variable information for the frame), then the whole stack trace computation is stopped.

Instead, we should catch any errors when we are calculating an individual frame, and skip adding it if it fails.