Prevent exception when removing nonexistent file from a ramdisk fragment. am: 67698d1888

Original change: https://android-review.googlesource.com/c/platform/tools/treble/+/3324375

Change-Id: Ie675698ddd656568df07ffbaeb11b62a14e1c9a0
Signed-off-by: Automerger Merge Worker <[email protected]>