Exception handlers may have null type arrays.

runtime/vm/precompiler.cc

Index: runtime/vm/precompiler.cc
diff --git a/runtime/vm/precompiler.cc b/runtime/vm/precompiler.cc
index 7e5fb37c48b95f963540f5fbbd2064bba1d49b77..a02c459a26c59e353434ec30b8d9c4899b02ded9 100644
--- a/runtime/vm/precompiler.cc
+++ b/runtime/vm/precompiler.cc
@@ -581,9 +581,11 @@ void Precompiler::AddTypesOf(const Function& function) {
       Array& types = Array::Handle(Z);
       for (intptr_t i = 0; i < handlers.num_entries(); i++) {
         types = handlers.GetHandledTypes(i);
-        for (intptr_t j = 0; j < types.Length(); j++) {
-          type ^= types.At(j);
-          AddType(type);
+        if (!types.IsNull()) {
+          for (intptr_t j = 0; j < types.Length(); j++) {
+            type ^= types.At(j);
+            AddType(type);
+          }
         }
       }
     }