area chart now detects if fill axis or axis origin are needed but not set

gist-charts/source/implementations/charts/areaChartImplementation.class.ts

@@ -84,6 +84,14 @@ export class AreaChartImplementation extends BaseChartImplementation {
         const ctx = me.canvas.context;
         let startingIndex = me.drawnData.length;
         const list = me.chart.datalist();
+        if ( me.chart.shouldFillToOrigin ) {
+            if ( !me.chart.fillAxis ) {
+                throw 'GistCharts: AreaChart Usage Error. If shouldFillToOrigin is true than fillAxis must also be defined';
+             }
+            if ( !me.chart.axisOrigin ) {
+                throw 'GistCharts: AreaChart Usage Error. If shouldFillToOrigin is true than axisOrigin must also be defined';
+            }
+         }
         while ( me.drawnData.length < list.length && me.drawnData.length - startingIndex < me.chart.drawCountPerRender ) {
             let line = me.processLine( list[ me.drawnData.length ] );
             ctx.beginPath();