pagesInCurrentSpineCount is not correct sometimes.

[Damon0331]

When the app load the epub file first time and the app load the chapter 5（or other chapters） at the first time, sometimes it get the wrong pagesInCurrentSpineCount(this is wrong : totalWidtht == webView.bounds.size.width, pagesInCurrentSpineCount == 1), the pagesInCurrentSpineCount is wrong.