The ornamental design for a nebulizer, as shown and described.
FIG. 1 is a perspective view of a nebulizer showing my new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view of the nebulizer shown with an attachment.
The broken lines showing the attachment in FIG. 8 illustrates the environment of the claimed design and form no part thereof. All other broken lines illustrate portions of the nebulizer that form no part of the claimed design.