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
Change-Id: I151c18f428d040a4cd9f2fb497c731440bb9fda3
1 file changed