The ornamental design for gel candle, as shown and described.
FIG. 1 is a front perspective view of a gel candle showing my new design, wherein grape leaves and grapes are disposed within the votive vessel.
FIG. 2 is a right side perspective view thereof.
FIG. 3 is a rear perspective view thereof.
FIG. 4 is a left side perspective view thereof.
FIG. 5 is a top rear perspective view thereof.
FIG. 6 is a top front perspective view thereof; and,
FIG. 7 is a top perspective view thereof.
The single dashed lines represent outer portions of a gel candle, an inner vessel, a wick and vines connecting grapes and form no part of the claim. The characteristic feature of the design resides with the gel candle having materials embedded therein.