[commands] Fix RepeatCommand calling end() twice (#5261)

wpilibNewCommands/src/main/java/edu/wpi/first/wpilibj2/command/RepeatCommand.java

@@ -63,7 +63,12 @@ public class RepeatCommand extends CommandBase {
 
   @Override
   public void end(boolean interrupted) {
-    m_command.end(interrupted);
+    // Make sure we didn't already call end() (which would happen if the command finished in the
+    // last call to our execute())
+    if (!m_ended) {
+      m_command.end(interrupted);
+      m_ended = true;
+    }
   }
 
   @Override