Fix a bug in Dbg::GetClassDescriptor.

The callers were incorrectly assuming we always returned a descriptor, which
isn't true when handed bad input.

Change-Id: I5509d18d8c234d97fa5ec2e0a01d4cdb44acfc55
diff --git a/src/jdwp/jdwp_event.cc b/src/jdwp/jdwp_event.cc
index d68d011..b688993 100644
--- a/src/jdwp/jdwp_event.cc
+++ b/src/jdwp/jdwp_event.cc
@@ -726,7 +726,7 @@
   basket.classId = pLoc->classId;
   basket.thisPtr = thisPtr;
   basket.threadId = Dbg::GetThreadSelfId();
-  basket.className = DescriptorToName(Dbg::GetClassDescriptor(pLoc->classId).c_str());
+  basket.className = Dbg::GetClassName(pLoc->classId);
 
   /*
    * On rare occasions we may need to execute interpreted code in the VM
@@ -924,7 +924,7 @@
   basket.pLoc = pThrowLoc;
   basket.classId = pThrowLoc->classId;
   basket.threadId = Dbg::GetThreadSelfId();
-  basket.className = DescriptorToName(Dbg::GetClassDescriptor(basket.classId).c_str());
+  basket.className = Dbg::GetClassName(basket.classId);
   basket.excepClassId = exceptionClassId;
   basket.caught = (pCatchLoc->classId != 0);
   basket.thisPtr = thisPtr;
@@ -1007,7 +1007,7 @@
   memset(&basket, 0, sizeof(basket));
   basket.classId = refTypeId;
   basket.threadId = Dbg::GetThreadSelfId();
-  basket.className = DescriptorToName(Dbg::GetClassDescriptor(basket.classId).c_str());
+  basket.className = Dbg::GetClassName(basket.classId);
 
   /* suppress class prep caused by debugger */
   if (InvokeInProgress()) {