Fix Subtypes::getMaxDepths

src/ir/subtypes.h

@@ -128,6 +128,8 @@ struct SubTypes {
         case HeapTypeKind::Cont:
           WASM_UNREACHABLE("TODO: cont");
         case HeapTypeKind::Import:
+          basic = type.getImport().bound;
+          break;
         case HeapTypeKind::Basic:
           WASM_UNREACHABLE("unexpected kind");
       }