The ornamental design for a muddler, as shown and described.
1. Muddler
1.1: Perspective
1.2: Front view, identical to back, left and right views
1.3: Top
1.4: Bottom
Fig. 1.1is a perspective view of a muddler in accordance with our new design; fig. 1.2is a front view thereof, where the back, left and right views are identical to the front view; fig. 1.3is a top view thereof; and fig. 1.4is a bottom view thereof.