fix($sce): do not assume $document[0] exists

[shahata]

this is important so that people can mock $window without having to add stuff that angular uses internally into it

Closes #9661

[petebacondarwin]

I feel a little uncomfortable modifying this way.
How about we change it to use msie instead? Especially now we use DocumentMode to set it any way.

[shahata]

The problem with using msie is that it will break the unit tests that expects this error to happen. We could fiddle with the msie during this test to force this to happen, but I feel more uncomfortable about that... Another option is to add an option to mock msie, but I'm not sure it is worth it since this is the only place we need it. (see the discussion in the original issue)

[shahata]

Also, the way I handled it is consistent with what we do in $SnifferProvider

[gkalpak]

@shahata : What do you mean by "this is the only place we need it" ?
It is used in bunch of places; this was just the only place that didn't use msie directly, but tried to use $document[0].documentMode.
This seems rather inconsistent (to me). I would prefer to always determine IE version in the same way (i.e. grobal msie) and preferably also have a way to mock it.

Why don't we use $sniffer.msie (as we did previously) anyway ?

[shahata]

I mean this is the only place we need to mock msie, so I'm not sure if it is worth to add something like $sniffer.msie just for this issue. @petebacondarwin WDYT? I can easily add support for mocking msie to this PR if it makes sense.

[petebacondarwin]

I would rather use msie and change the tests that mock it. Keep all the msie stuff in one place.

[petebacondarwin]

We will need this as ngScenario gets compiled up into a separate file with its own closure.
It just happens that our unit tests run with all the files in a single closure! (Which is bad but no one has the energy to fix it)