LocalFile: avoid hard failures on non-existing files.

LocalFile: avoid hard failures on non-existing files.

Some methods on LocalFile will fatal if called on a non-existing file.
ApiQueryImageInfo did not take that into account.

This patch changes LocalFile to avoid fatal errors, and ApiQueryImageInfo
to not try and report information on non-existing files.

NOTE: the modified code has NO test coverage! This should be fixed
before this patch is applied, or the patch needs to be thoroughly tested
manually.

Bug: T221812
Change-Id: I9b74545a393d1b7a25c8262d4fe37a6492bbc11e