The ornamental design for an instrumentpanel for an automobile, as shown and described.
FIG. 1 is a perspective view of an instrument panel for an automobile showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines depict boundaries of the claimed design and form no part of the claimed design; the lightened portions within the broken lines depict portions of the instrument panel for an automobile that form no part of the claimed design.