https://github.com/leeoniya/uPlot/compare/1.6.1...1.6.2

• series.isGap is gone and uPlot.join() now returns the data array directly, with undefined occupying the value locations of alignment artifacts. as a result, .join() internals have been optimized/simplified for a 2-3x speedup.
• callback signatures for axis.stroke, axis.grid.stroke, axis.ticks.stroke
• no more defaulting to black when series.stroke is absent. this helps fill-only series.
• some more robustness to early-exit before trying to draw will empty stroke, empty fill or empty paths.