is one piece episode 501 filler?

The episode starts where the previous episode ended, where Sabo is being chased by his father's men. Sabo keeps falling over which allowed his father's men to catch him.

Sabo fails to warn his brothers about the fire. Bluejam reveals to Ace and Luffy that there will be a fire at the Gray Terminal, also saying that he is not the mastermind of this operation.

Now that Ace and Luffy know about the plan, Bluejam asks if they have any hidden treasure.