The ornamental design of a humidifier, as shown and described.
FIG. 1 is a top perspective view of humidifier showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a top plan view thereof; and,
FIG. 4 is a side elevation view thereof, the opposite side being a mirror
image thereof.
The rear and bottom view of the embodiment form no part of the claimed
design. The broken line showing of environmental structure in FIGS. 1-4 is
for illustrative purposes only and forms no part of the claimed design.