empty reporter and boolean blocks are invalid

[pdawyndt]

A warning should be issued when using an empty reporter block (()) or an an empty boolean block (<>) since Blockly does not allow this; it automatically assignes names to these blocks ((a), (b), ...). The logic should than be that

say {}

generates a say block without a shadow (@Ellen102 can you add a graphical example of this) and

say {""} 

or

say "" 

generates a say block with a shadow; the options

say {()}
say ()
say {<>}
say <> 

are illigal and should issue a warning, because empty reporters and booleans are not supported because of the automatic naming of Google Blockly; as a recovery a block with a %1 placeholder be issued