Frameworks: Fix NPE for agent attach

Fix missing null check.

Bug: 62445317
Test: m
Test: adb shell am start --attach-agent dummy.so
Test: m cts && cts-tradefed run commandAndExit cts-dev --module CtsJvmtiAttachingHostTestCases
Change-Id: Ia16c2973b24f81839d20502339978e75a23a93bc
1 file changed