The ornamental design for a packagingblank, as shown and described.
The application file contains at least one drawing executed in color. Copies of this patent with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
FIG. 1 is a top plan view of a packaging blank showing our new design; and,
FIG. 2 is a side elevation view thereof.
The dashed broken lines in the drawings illustrate portions of the packaging blank that form no part of the claimed design.