/execute run does not cause syntax error when arguments are missing

The bug

/execute run does not cause a syntax error when the command to run is missing arguments. There is no feedback at all in this case.
However, it is considered a syntax error if the command to run does not exit.

How to reproduce

Compare the result when typing / executing the following commands.

1. Invalid command:

   /execute run scoreboard invalid

   ✔ An error is shown

2. Missing argument:

   /execute run scoreboard objectives

   ❌ No error message, no feedback at all