The ornamental design for a columnprotector, as shown and described.
Figure 1.1 is a perspective view of a column protector;
Figure 1.2 is a front view thereof; and
Figure 1.3 is another perspective view thereof shown in an unfolded position of use.
The broken lines shown in Figures 1.1-1.3 illustrate portions of the column protector that form no part of the claimed design. The additional broken lines show in Figure 1.3 illustrates environment and forms no part of the claimed design.