message: fix: gradient bug when no data is set
  fix and close ecomfe/echarts#7731
diff: @@ -27,6 +27,12 @@ function createLinearGradient(ctx, obj, rect) {
  y2 = y2 * rect.height + rect.y;
  }
  + // Fix NaN when rect is Infinity
  + x = isNaN(x) ? 0 : x;
  + x2 = isNaN(x2) ? 1 : x2;
  + y = isNaN(y) ? 0 : y;
  + y2 = isNaN(y2) ? 0 : y2;
  +
  var canvasGradient = ctx.createLinearGradient(x, y, x2, y2);
  return canvasGradient;
  