Edit if condition to check for embedded resources

[duskybomb]

We can merge this. It was my initial commit to branch issue/16

[m3nu]

Here is the issue with this PR:

• \EmbeddedFiles is contained in \Names
• We want to fail if \Names doesn't exist. If \Names doesn't exist, \EmbeddedFiles also can't exist.
• The way you wrote it is confusing.
• The correct way would be to:

1. check for \Names.
2. If \Names exists, check for \EmbeddedFiles.

By doing this you can take advantage of the fact that Python checks AND conditions from left to right.

[duskybomb]

You mean I should use nested if?

[m3nu]

Using an and would be clearest. But it's fine. If it fixes your issue, let's merge it. I didn't realize this is only a very minor check before reading the XML.

I also don't like too many nots. This is generally a sign of bad layout.