Add a check for null thread before trying to suspend

The patch fixes a jpda test failure due to a failed
assertion in SuspendThreadByThreadId. There should be
a check for a null thread before the assertion check.
This was the behavior of previous code (4.4.2) where
this test passes, but this check was removed during
some refactoring of the code.

Change-Id: Ia63de5f159ce1e51110bf9dc604011d07b2f048e
Signed-off-by: Johnnie Birch <johnnie.l.birch.jr@intel.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc b/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
index 5d90f1a..e17e60a 100644
--- a/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
+++ b/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
@@ -52,9 +52,15 @@ static jobjectArray DdmVmInternal_getStackTraceById(JNIEnv* env, jclass, jint th
     jobject internal_trace = self->CreateInternalStackTrace<false>(soa);
     trace = Thread::InternalStackTraceToStackTraceElementArray(soa, internal_trace);
   } else {
-    // Suspend thread to build stack trace.
     ThreadList* thread_list = Runtime::Current()->GetThreadList();
     bool timed_out;
+
+    // Check for valid thread
+    if (thin_lock_id == ThreadList::kInvalidThreadId) {
+      return nullptr;
+    }
+
+    // Suspend thread to build stack trace.
     Thread* thread = thread_list->SuspendThreadByThreadId(thin_lock_id, false, &timed_out);
     if (thread != nullptr) {
       {