Many existing .blend files (including startup ones) seem to have invalid
embedded IDs (they are not properly tagged with `LIB_EMBEDDED_DATA`).
We cannot `do_version` this so just fix it on the fly when detecting the
issue. User then need to re-save these files.
We also need to update some release files (default factory startup is
OK, but e.g. the VSE template one is not).
Keeping the assert is important here, as such missing flag is a critical
data corruption that can potentially have many serious consequences
throughout the ID management code.
e46687c3aa