[5.5] Ignore svg's in validateDimensions()

[tobz-nz]

SVG dimensions are pretty irrelevant, so they should simply pass this test.

If this approach is too simple, we could check against the svg's width/height or viewBox attributes to do an actual size test. Although this is probably not valid in some cases (a sprite svg with many <symbol>'s of different sizes for example)

[Kyslik]

What happens if file has no "ext" but mime is svg?

[m1guelpf]

@tobz-nz I believe this is a breaking change, as it will change the way validation affects an uploaded svg file.

[tobz-nz]

So the feedback I'm taking from your comments is:

• change the logic to check mimetype instead of extension
• PR to the master branch

Is this correct?
Just a little unclear on steps forward.

[m1guelpf]

You should definitely send this to the master branch.

[tobz-nz]

The master branch has not been updated in 3 years... is it really the right branch to PR to?

[tobz-nz]

Created new PR #21390 to the master branch, with the check changed to match the mimeType.