fixup (add isGL2D in heatmap calc)

Author: etpinard

src/traces/heatmap/calc.js

@@ -172,6 +172,7 @@ function makeBoundArray(trace, arrayIn, v0In, dvIn, numbricks, ax) {
     var arrayOut = [],
         isContour = Plots.traceIs(trace, 'contour'),
         isHist = Plots.traceIs(trace, 'histogram'),
+        isGL2D = Plots.traceIs(trace, 'gl2d'),
         v0,
         dv,
         i;