Auto crop fix

[hugleo]

After some tests with the said document from #970 it seems like that the visual defect occurs for only semi-auto and manual crop modes.

I've removed auto-crop from the rule so #4106 can be fixed when using auto-crop.

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This change is 

[Frenzie]

lgtm, might be worth adding some parentheses for clarity even though it makes no functional difference?

[hugleo]

If someone wants to dig more on this later I'm sending two test files, same content and dimensions.
test_document.pdf
test_document.djvu (Similar behavior to #970 said file)

If someone wants to know the problem that #970 fixed, follow:
The tests are with 970 reverted back.
Effect of executing self.view:onBBoxUpdate(ubbox_dimen) for all cases.
For the tests here we open the document with all settings empty for each test, apply the crop mode on page 1 and move to page 2. The images show a bit of page 1 and the defect on page 2.

for test_document.pdf
semi-auto crop
Looks normal

manual crop
Visual defect occurs (looks more or less)

for test_document.djvu
semi-auto crop
Visual defect occurs

manual crop
Visual defect occurs

Interesting for pdf we got the visual defect only for manual crop. Because djvu fails for semi-auto and manual crop modes, I'm keeping #970 for both. So #4106 will look fine for auto-crop but will still fail for semi-auto crop, unless we choose to throw the semi-auto crop problem on djvu side.

tests.zip

[Frenzie]

I just meant the first one really, on the second it looks weird. :-P

But pinging @poire-z for some thoughts.

[poire-z]

I don't mind the parens around the second one. It looks balanced, and may save 500ms of brain processing power while reading :)