diff --git a/frontend/src/components/gantt/primitives/GanttChartPrimitive.vue b/frontend/src/components/gantt/primitives/GanttChartPrimitive.vue
index 514648361..e5454ba0a 100644
--- a/frontend/src/components/gantt/primitives/GanttChartPrimitive.vue
+++ b/frontend/src/components/gantt/primitives/GanttChartPrimitive.vue
@@ -35,9 +35,12 @@ const focusedCellIndex = ref<number | null>(null)
 const focusedRow = computed(() => focusedRowIndex.value === null
 	? null
 	: props.rows[focusedRowIndex.value])
-const cellsCount = computed(() => props.rows.length 
-	? props.cellsByRow[props.rows[0]].length 
-	: 0)
+const cellsCount = computed(() => {
+	const firstRow = props.rows[0]
+	return firstRow !== undefined && props.cellsByRow[firstRow]
+		? props.cellsByRow[firstRow].length
+		: 0
+})
 
 onClickOutside(chartRef, () => {
 	focusedRowIndex.value = null
@@ -63,7 +66,7 @@ function initializeFocus() {
 	if (focusedRowIndex.value === null && props.rows.length > 0) {
 		focusedRowIndex.value = 0
 		focusedCellIndex.value = 0
-		emit('update:focused', { row: focusedRow.value, cell: focusedCellIndex.value })
+		emit('update:focused', { row: focusedRow.value ?? null, cell: focusedCellIndex.value })
 	}
 }
 
@@ -72,7 +75,7 @@ function setFocus(rowId: string, cellIndex: number = 0) {
 	if (rowIndex !== -1) {
 		focusedRowIndex.value = rowIndex
 		focusedCellIndex.value = Math.max(0, Math.min(cellIndex, cellsCount.value - 1))
-		emit('update:focused', { row: focusedRow.value, cell: focusedCellIndex.value })
+		emit('update:focused', { row: focusedRow.value ?? null, cell: focusedCellIndex.value })
 	}
 }