The ornamental design for a laddertopcap, as shown and described.
FIG. 1 is a perspective view of a ladder top cap illustrating my new design, with portions of the ladder top cap being shown in broken lines, which broken lines are for illustrative purposes only and form no part of the claimed design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right-side elevational view thereof, with the left-side elevational view thereof substantially similar;
FIG. 4 is a top plan view thereof, with portions of the ladder top cap being shown in broken lines, which broken lines are for illustrative purposes only and form no part of the claimed design;
FIG. 5 is a rear elevation view thereof;
FIG. 6 is a bottom view thereof, with portions of the ladder top cap being shown in broken lines, which broken lines are for illustrative purposes only and form no part of the claimed design.