The ornamental design for a protective headband, as shown and described.
FIG. 1 is a perspective view of a protective head band showing our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The partial human figure depicted by broken lines represents environmental subject matter included to better illustrate how the design may appear when worn. The drawstring shown in broken lines represents environmental structure. None of the broken-line matter forms a part of the claimed design.