Resolves TypeError: Cannot read property viewRangeLength of undefined

Fixes eclipse-cdt-cloud#104

Signed-off-by: Ankush Tyagi <ankush.tyagi@ericsson.com>

timeline-chart/src/layer/time-graph-chart.ts

@@ -6,6 +6,7 @@ import { TimelineChart } from "../time-graph-model";
 import { TimeGraphComponent, TimeGraphRect, TimeGraphStyledRect } from "../components/time-graph-component";
 import { TimeGraphChartLayer } from "./time-graph-chart-layer";
 import { TimeGraphRowController } from "../time-graph-row-controller";
+import { TimeGraphUnitController } from "../time-graph-unit-controller";
 import { TimeGraphAnnotationComponent, TimeGraphAnnotationComponentOptions, TimeGraphAnnotationStyle } from "../components/time-graph-annotation";
 
 export interface TimeGraphRowElementMouseInteractions {
@@ -41,6 +42,7 @@ export class TimeGraphChart extends TimeGraphChartLayer {
     protected rowElementMouseInteractions: TimeGraphRowElementMouseInteractions;
     protected selectedElementModel: TimelineChart.TimeGraphState;
     protected selectedElementChangedHandler: ((el: TimelineChart.TimeGraphState) => void)[] = [];
+    protected unitController: TimeGraphUnitController;
 
     protected providedRange: TimelineChart.TimeGraphRange;
     protected providedResolution: number;
@@ -172,14 +174,16 @@ export class TimeGraphChart extends TimeGraphChartLayer {
                 this.maybeFetchNewData();
             }
         });
-        if (this.unitController.viewRangeLength) {
+        if (this.unitController.viewRangeLength && this.stateController.canvasDisplayWidth) {
             this.maybeFetchNewData();
         }
     }
 
     updateChart() {
         const update = true;
-        this.maybeFetchNewData(update);
+        if (this.unitController && this.stateController) {
+            this.maybeFetchNewData(update);
+        }
     }
 
     update() {