The ornamental design for a mop connector, as shown and described.
FIG. 1 is a top view of a mop connector showing our new design;
FIG. 2 is a bottom view of the mop connector;
FIG. 3 is a front view of the mop connector;
FIG. 4 is a rear view of the mop connector;
FIG. 5 is a left side view of the mop connector;
FIG. 6 is a right side view of the mop connector; and,
FIG. 7 is a front perspective view of the mop connector as attached to a bundle of strings.
The broken lines in FIGS. 1 and 2 form no part of the claimed design. The broken lines in FIG. 7 represent environment of the mop connector and form no part of the claimed design.