fixed wrong eater content when loading native EM levels

fixed wrong eater content when loading native EM levels

This fixes a regression bug from commit baf962d5 that causes wrong
eater content when loading native EM levels.

Native Emerald Mine levels before version V5 only supported 28 eater
objects, but some levels contained object codes above that, which are
now mapped to empty space. (Before, they were mapped to the first 32
eater objects (28 objects, padded with four empty space objects) using
"mod 32" operation, which lead to completely wrong eater objects for
nearly all affected levels.)

Mapping these eater objects to empty space is the best solution for
now, as nearly all affected levels are solvable when using empty space
objects instead (as most of these objects originally mapped to doors
or letter elements).