Fix handling for partial cdex conversion rejection in multidex

In the case where some dex files for multidex were rejected by cdex
conversion for having duplicate ids (or other reasons), there was a
failing assert.

This change fixes the assert by skipping the dex file instead.

Test: test-art-host-gtest-dex2oat_test
Bug: 73126133

Change-Id: I05f560118d7a8d9363334f1349e2b75171f1e26d