fix

frontend/src/views/ActivitiesView.vue

@@ -3,7 +3,6 @@ import { onMounted, ref } from 'vue'
 import { useActivitiesStore } from '../stores/activities'
 import { useRouter } from 'vue-router'
 import Card from 'primevue/card'
-import Button from 'primevue/button'
 import FileUpload from 'primevue/fileupload'
 import Tag from 'primevue/tag'
 import ProgressSpinner from 'primevue/progressspinner'

frontend/src/views/ActivityDetailView.vue

@@ -425,7 +425,7 @@ onMounted(async () => {
         <Card v-if="zones?.power_zones?.length">
           <template #title>Power Zones</template>
           <template #content>
-            <VChart :option="buildZonesChart()" style="height: 250px" autoresize />
+            <VChart :option="buildZonesChart() ?? undefined" style="height: 250px" autoresize />
           </template>
         </Card>
 
@@ -433,7 +433,7 @@ onMounted(async () => {
         <Card v-if="zones?.hr_zones?.length">
           <template #title>Heart Rate Zones</template>
           <template #content>
-            <VChart :option="buildHrZonesChart()" style="height: 200px" autoresize />
+            <VChart :option="buildHrZonesChart() ?? undefined" style="height: 200px" autoresize />
           </template>
         </Card>
 
@@ -441,7 +441,7 @@ onMounted(async () => {
         <Card v-if="powerCurve?.curve && Object.keys(powerCurve.curve).length > 0">
           <template #title>Power Curve</template>
           <template #content>
-            <VChart :option="buildPowerCurveChart()" style="height: 250px" autoresize />
+            <VChart :option="buildPowerCurveChart() ?? undefined" style="height: 250px" autoresize />
           </template>
         </Card>
       </div>

frontend/src/views/DashboardView.vue

@@ -6,7 +6,6 @@ import { useCoachingStore } from '../stores/coaching'
 import type { FitnessEntry, WeeklyStats, PersonalRecord, TodayWorkout } from '../types/models'
 import Card from 'primevue/card'
 import Tag from 'primevue/tag'
-import Button from 'primevue/button'
 import { useRouter } from 'vue-router'
 import { use } from 'echarts/core'
 import { CanvasRenderer } from 'echarts/renderers'
@@ -252,7 +251,7 @@ onMounted(async () => {
     <Card v-if="fitness.length > 0" class="mb-8">
       <template #title>Fitness Trend</template>
       <template #content>
-        <VChart :option="buildFitnessChart()" style="height: 280px" autoresize />
+        <VChart :option="buildFitnessChart() ?? undefined" style="height: 280px" autoresize />
         <div class="flex items-center justify-center gap-6 mt-2 text-xs text-surface-500">
           <span>CTL: chronic training load (fitness)</span>
           <span>ATL: acute training load (fatigue)</span>
@@ -265,7 +264,7 @@ onMounted(async () => {
     <Card v-if="weeklyStats.length > 0" class="mb-8">
       <template #title>Weekly Summary</template>
       <template #content>
-        <VChart :option="buildWeeklyChart()" style="height: 280px" autoresize />
+        <VChart :option="buildWeeklyChart() ?? undefined" style="height: 280px" autoresize />
       </template>
     </Card>