[automerge] Add defensive try-catch to ModelDownloader inside TCS. 2p: af378fae69

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libtextclassifier/+/16931243

Bug: 219998215
Change-Id: I8c8ada678a557b4903deb188e01b9f197278ec4d