fix: guard getBorders() against empty lines input

src/main/ts/ingrid.ts

@@ -67,14 +67,16 @@ export const parseLines = (input: string, sep?: string): TLineDigest[] =>
 
 const countWordsByIndex = ({words}: TLineDigest, index: number): number => words.filter(({e}) => e < index).length
 
-export const getBorders = (lines: TLineDigest[]): number[] =>
-  lines[0].spaces.reduce<number[]>((m, i) => {
+export const getBorders = (lines: TLineDigest[]): number[] => {
+  if (lines.length === 0) return []
+  return lines[0].spaces.reduce<number[]>((m, i) => {
     const c = countWordsByIndex(lines[0], i)
     if (lines.every(l => l.spaces.includes(i) && c === countWordsByIndex(l, i))) {
       m.push(i)
     }
     return m
   }, [])
+}
 
 // eslint-disable-next-line sonarjs/cognitive-complexity
 export const parseUnixGrid = (input: string): TIngridResponse => {

src/test/ts/ingrid.test.ts

@@ -67,6 +67,11 @@ a   b    c
     const result = getBorders(lines)
     assert.deepEqual(result, [3, 7, 8])
   })
+
+  it('returns empty array for empty input', () => {
+    const result = getBorders([])
+    assert.deepEqual(result, [])
+  })
 })
 
 describe('parse()', () => {