ART: Fix null dereference for JSR45

Avoid dereferencing DEX cache pointer if it is null. Arrays and
primitive types do not have DEX cache's installed.

Test: art/tools/run-jdwp-tests.sh --mode=host
Bug: 38126955

(Cherry pick from commit cf7127b4a368ed26eaf257286173d5337f67a0a7)

Change-Id: Ie9219c688d009d28d090a75913af86d5d3ee7df6
1 file changed