When a catch is unreachable, use the canonical empty array instead of null as its type array.

runtime/vm/precompiler.cc

Index: runtime/vm/precompiler.cc
diff --git a/runtime/vm/precompiler.cc b/runtime/vm/precompiler.cc
index 2f876e09dffec936f0220d4f43b4cd304f284ffc..3743b1efe72e1f0904c7a17b47596758c05ab328 100644
--- a/runtime/vm/precompiler.cc
+++ b/runtime/vm/precompiler.cc
@@ -581,11 +581,9 @@ 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);
-        if (!types.IsNull()) {
-          for (intptr_t j = 0; j < types.Length(); j++) {
-            type ^= types.At(j);
-            AddType(type);
-          }
+        for (intptr_t j = 0; j < types.Length(); j++) {
+          type ^= types.At(j);
+          AddType(type);
         }
       }
     }