Fix init: access non-init in run test
Fix init: access non-init in run test

```Scala
-- Error: tests/run/tuples1.scala:28:27 ----------------------------------------
28 |  val c0_1 = x0 ++ x1; val c0_1c: Int *: Unit = c0_1c; println(s"c0_1 = $c0_1")
   |                           ^
   |Access non-initialized field value c0_1c. Calling trace:
   | -> val c0_1 = x0 ++ x1; val c0_1c: Int *: Unit = c0_1c; println(s"c0_1 = $c0_1")	[ tuples1.scala:28 ]
-- Error: tests/run/tuples1.scala:29:27 ----------------------------------------
29 |  val c1_0 = x1 ++ x0; val c1_0c: Int *: Unit = c1_0c; println(s"c1_0 = $c1_0")
   |                           ^
   |Access non-initialized field value c1_0c. Calling trace:
   | -> val c1_0 = x1 ++ x0; val c1_0c: Int *: Unit = c1_0c; println(s"c1_0 = $c1_0")	[ tuples1.scala:29 ]
```

sjrd/dotty,sjrd/dotty,dotty-staging/dotty,lampepfl/dotty,sjrd/dotty,dotty-staging/dotty,sjrd/dotty,sjrd/dotty,som-snytt/dotty,lampepfl/dotty,som-snytt/dotty,dotty-staging/dotty,lampepfl/dotty,som-snytt/dotty,dotty-staging/dotty,dotty-staging/dotty,lampepfl/dotty,lampepfl/dotty,som-snytt/dotty,som-snytt/dotty