Also always clear the UUIDs first so that shorter strings don't leave
data undefined.

Bug b/116336664

Change-Id: I77d5ae1514db5d68d540614b7c57c4872695ecca
Reviewed-on: https://swiftshader-review.googlesource.com/c/22490Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Corentin Wallez <cwallez@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>