is one piece episode 237 filler?

Usopp is alone on the Going Merry, reflecting on how Luffy defeated him and left him behind. Meanwhile, the crowd investigates an incident.

On top of a building, Sanji and Chopper were about to start searching the town for Robin, before Nami interrupts and tells Luffy that Iceburg was shot in his own home, with the only clue being an ornate mask at the scene. Kaku and Lulu were speculating on who was responsible, suspecting Corgi of the World Government, while the citizens suspect the Franky Family and the Big Helmet Pirates.