We claim the ornamental design for a sealing gun, as shown and described.
FIG. 1 is a front perspective view of a sealing gun of the present invention;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines throughout the figures are directed to portions of the sealing gun that form no part of the claim. Additionally, the unevenly broken lines in the drawings define the limits of the claimed design.