I claim the ornamental design for a trampoline safety system, and shown and described.
FIG. 1 is a perspective view of a trampoline safety system, including the inwardly curved legs of system.
FIG. 2 is a side elevation view thereof.
FIG. 3 is a top plan view thereof; and,
FIG. 4 is a bottom plan view thereof.
The broken line showing of the trampoline safety system is for the purpose of illustrating portions of the article that form no part of the claimed design.