Add undefined check in contentAsDataUrl to prevent unhandled exceptions
Add undefined check in contentAsDataUrl to prevent unhandled exceptions

ContentProvider.contentAsDataURL previously only contained an explicit '=== null' check for the content parameter before accessing content.length.

This CL adds an undefined check in addition to the null check to prevent unhandled exceptions.

Change-Id: Ic93bbb085cff45ffd91ef07fc0b4d710c546b8cc
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/1978972
Reviewed-by: Robert Paveza <7787129de3d0cb4911c68d958db3023863584560@microsoft.com>
Commit-Queue: Connor Moody <47157f9d3532dd814e833abfecde0669ceb3aa23@microsoft.com>

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