chore: resolve lint issues

Signed-off-by: hainenber <dotronghai96@gmail.com>

superset-frontend/plugins/plugin-chart-echarts/test/MixedTimeseries/transformProps.test.ts

@@ -431,5 +431,5 @@ test('should add a formula annotation when X-axis column has dataset-level label
   expect(formulaSeries).toBeDefined();
   expect(formulaSeries?.data).toBeDefined();
   expect(Array.isArray(formulaSeries?.data)).toBe(true);
-  expect((formulaSeries?.data as unknown[]).length).toBeGreaterThan(0);
+  expect((formulaSeries?.data as unknown[])?.length).toBeGreaterThan(0);
 });

superset-frontend/plugins/plugin-chart-echarts/test/Timeseries/transformProps.test.ts

@@ -304,8 +304,8 @@ describe('EchartsTimeseries transformProps', () => {
     expect(formulaSeries).toBeDefined();
     expect(formulaSeries?.data).toBeDefined();
     expect(Array.isArray(formulaSeries?.data)).toBe(true);
-    expect((formulaSeries?.data as unknown[]).length).toBeGreaterThan(0);
-    const firstDataPoint = (formulaSeries?.data as [number, number][])[0];
+    expect((formulaSeries?.data as unknown[])?.length).toBeGreaterThan(0);
+    const firstDataPoint = (formulaSeries?.data as [number, number][])?.[0];
     expect(firstDataPoint).toBeDefined();
     expect(firstDataPoint[1]).toBe(firstDataPoint[0] * 2);
   });
@@ -384,7 +384,7 @@ describe('EchartsTimeseries transformProps', () => {
       result.echartOptions.series as SeriesOption[] | undefined
     )?.find((s: SeriesOption) => s.name === 'My Formula');
     expect(formulaSeries).toBeDefined();
-    const firstDataPoint = (formulaSeries?.data as [number, number][])[0];
+    const firstDataPoint = (formulaSeries?.data as [number, number][])?.[0];
     expect(firstDataPoint).toBeDefined();
     expect(firstDataPoint[0]).toBe(firstDataPoint[1] * 2);
   });

superset-frontend/src/explore/components/ExploreChartPanel/index.tsx

@@ -113,8 +113,10 @@ const Styles = styled.div<{ showSplite: boolean }>`
   }
 
   .gutter {
-    border-top: 1px solid ${({ theme }) => theme.colorSplit};
-    border-bottom: 1px solid ${({ theme }) => theme.colorSplit};
+    border-top: 1px solid
+      color-mix(in srgb, ${({ theme }) => theme.colorSplit}, black 15%);
+    border-bottom: 1px solid
+      color-mix(in srgb, ${({ theme }) => theme.colorSplit}, black 15%);
     width: ${({ theme }) => theme.sizeUnit * 9}px;
     margin: ${({ theme }) => theme.sizeUnit * GUTTER_SIZE_FACTOR}px auto;
   }