The ornamental design for a baby's finger saver, as shown and described.
FIG. 1 is a perspective view of a baby's finger saver showing my new design spaced from a modified door.
FIG. 2 is a front elevation view thereof, the rear elevation view a mirror image thereof.
FIG. 3 is a right side elevation view thereof.
FIG. 4 is a left side elevation view thereof; and,
FIG. 5 is a top plan view thereof, the bottom plan view a mirror image thereof.
The broken lines shown in the drawings represent environmental structure and form no part of the claimed design. The baby's finger saver shown in FIGS. 2, 3, 4 are shown broken apart for ease of illustration.