correct hook name.

src/BaseCharts/Bar.js

@@ -55,7 +55,7 @@ export default Vue.extend({
       this._chart.generateLegend()
     }
   },
-  destroy () {
+  beforeDestroy () {
     this._chart.destroy()
   }
 })

src/BaseCharts/Doughnut.js

@@ -38,7 +38,7 @@ export default Vue.extend({
       this._chart.generateLegend()
     }
   },
-  destroy () {
+  beforeDestroy () {
     this._chart.destroy()
   }
 })

src/BaseCharts/Line.js

@@ -53,7 +53,7 @@ export default Vue.extend({
       this._chart.generateLegend()
     }
   },
-  destroy () {
+  beforeDestroy () {
     this._chart.destroy()
   }
 })

src/BaseCharts/Pie.js

@@ -38,7 +38,7 @@ export default Vue.extend({
       this._chart.generateLegend()
     }
   },
-  destroy () {
+  beforeDestroy () {
     this._chart.destroy()
   }
 })

src/BaseCharts/PolarArea.js

@@ -38,7 +38,7 @@ export default Vue.extend({
       this._chart.generateLegend()
     }
   },
-  destroy () {
+  beforeDestroy () {
     this._chart.destroy()
   }
 })

src/BaseCharts/Radar.js

@@ -38,7 +38,7 @@ export default Vue.extend({
       this._chart.generateLegend()
     }
   },
-  destroy () {
+  beforeDestroy () {
     this._chart.destroy()
   }
 })