VM: Handle null-case when running with --trace-ic.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index c3624ce349b1e6dbe8c154e79cbed712002b4eea..f844cea3fb3d67f9f22daf7397b68a000f125181 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -767,7 +767,7 @@ static bool ResolveCallThroughGetter(const Instance& receiver,
     OS::PrintErr("InvokeField IC miss: adding <%s> id:%" Pd " -> <%s>\n",
         Class::Handle(receiver.clazz()).ToCString(),
         receiver.GetClassId(),
-        target_function.ToCString());
+        target_function.IsNull() ? "null" : target_function.ToCString());
   }
   *result = target_function.raw();
   return true;
@@ -800,7 +800,7 @@ RawFunction* InlineCacheMissHelper(
       OS::PrintErr("NoSuchMethod IC miss: adding <%s> id:%" Pd " -> <%s>\n",
           Class::Handle(receiver.clazz()).ToCString(),
           receiver.GetClassId(),
-          target_function.ToCString());
+          target_function.IsNull() ? "null" : target_function.ToCString());
     }
     result = target_function.raw();
   }