We claim the ornamental design for a vacuum cleaner, as shown and described.
FIG. 1 is a front perspective view of a vacuum cleaner showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a rear perspective view thereof; and,
FIG. 9 is enlarged view of encircled portion in FIG. 3.
The broken lines in the figures show portions of the vacuum cleaner which form no part of the claimed design. The dot-dash broken lines encircling portions of the claimed design that are illustrated in enlargements form no part of the claimed design.