Static else block references should be nulled out

[Rich-Harris]

REPL — the reference to the removed else block needs to be nulled out:

if ( each_block_value.length ) {
-  if ( each_block_else ) each_block_else.destroy( true );
+  if ( each_block_else ) {
+    each_block_else.destroy( true );
+    each_block_else = null;
+  }
} else if ( !each_block_else ) {
  each_block_else = create_each_block_else( root, component );
  each_block_else.mount( each_block_anchor.parentNode, each_block_anchor );
}