(bug 58976) Do not get() the item straight after preloading it.

The ItemPage.get() raises the NoPage exception if it does not exists.
It's not possible to catch this and return to the iterator:

try:
    for page in preloaditempages():
        # do something with page
except NoPage:
    # ??? No way to continue processing the next page

By removing the internal .get(), we allow the following:

for page in preloaditempages():
    # page is not guaranteed to exist now
    try:
        # do something with page
    except NoPage:
        # print an error
        continue # with the next page

Change-Id: I9e09ba42e4562a962731f6c2cca70c020901828f
Merge "(bug 58976) Do not get() the item straight after preloading it."