Fixed corner cases of svg-tag--cursor-function

[mkvoya]

This PR fixes two corner cases in svg-tag--cursor-function:

1. (+ (point) 1) might exceed the end of the buffer;
2. end might be nil.

[rougier]

Thanks. Can you reduce the PR? GitHub highlights some changes that do not appear to be actual change (I don't know why)
Also, can you sign the Emacs copyright assignment?

[mkvoya]

Thanks. Can you reduce the PR? GitHub highlights some changes that do not appear to be actual change (I don't know why)

That is because of the indent changes. I added a when clause which makes the code indent more.

Also, can you sign the Emacs copyright assignment?

I have sent the email and will update here later.