/time command reports success when no changes are made

The bug

/time set, /time add, /time pause, and /time resume all succeed even when no changes are made. Commands that have no effect due to no changes being made are supposed to report failure.

How to reproduce

1. Type /time pause twice

2. Type /time set 6000 twice

Expected results

The second time each command was typed, it should fail, since no changes were made

Observed results

It says “Paused clock” twice, and “set to 6000 ticks” twice