[Sources]: Bug fix where frontend is imporoperly handling a pausedEvent with empty callframes
[Sources]: Bug fix where frontend is imporoperly handling a pausedEvent with empty callframes

Issue:
- the DevTools crashes when trying to access "callFrame.script" on line 472 of DebuggerWorkspaceBinding.js
    - This is caused when there is no callframes in the callframes array
    - The DevTools should handle this scenario gracefully without crashing

Changes:
- returning false early in _beforePaused
    - This causes a "stepOver"/"stepInto" call and try to set the paused details at the new location

Bug: 1129220
Change-Id: I7d73aa9ff2b83298163e11516ec67450554ea39d
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2415235
Reviewed-by: Tony Ross <d5807c9a1621d46cc76cd6770054768aff0ae774@microsoft.com>
Reviewed-by: Jack Lynch <d6fb7cfbb8c8618e756350219cb7952a0ad656b7@microsoft.com>
Commit-Queue: Michael Liao <00d75d81082fdf74688ec453c516b42f7cbf0f40@microsoft.com>

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