Fix 107-int-math2 with interpreter.

Change-Id: I67fa946ed94cc0c8e48e3814ba9be0b48c970ef1
diff --git a/src/interpreter/interpreter.cc b/src/interpreter/interpreter.cc
index bff9f37..3b041c8 100644
--- a/src/interpreter/interpreter.cc
+++ b/src/interpreter/interpreter.cc
@@ -883,7 +883,8 @@
         break;
       }
       case Instruction::THROW: {
-        Throwable* t = shadow_frame.GetVRegReference(dec_insn.vA)->AsThrowable();
+        Object* o = shadow_frame.GetVRegReference(dec_insn.vA);
+        Throwable* t = (o == NULL) ? NULL : o->AsThrowable();
         self->DeliverException(t);
         break;
       }