Ensure quote do not contain Hole body

Author: nicolasstucki

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -664,6 +664,7 @@ object TreeChecker {
         assert(tree.tags.isEmpty, i"unexpected tags in Quote before staging phase: ${tree.tags}")
       else
         assert(!tree.body.isInstanceOf[untpd.Splice] || inInlineMethod, i"missed quote cancellation in $tree")
+        assert(!tree.body.isInstanceOf[untpd.Hole] || inInlineMethod, i"missed quote cancellation in $tree")
         if StagingLevel.level != 0 then
           assert(tree.tags.isEmpty, i"unexpected tags in Quote at staging level ${StagingLevel.level}: ${tree.tags}")