Keep the original line number if no source map

src/index.js

@@ -102,7 +102,7 @@ module.exports = options => ({
           // Replace "brace" with "backtick" in warnings, e.g.
           // "Unexpected empty line before closing backtick" (instead of "brace")
           text: warning.text.replace(/brace/, 'backtick'),
-          line: lineCorrection[warning.line]
+          line: lineCorrection[warning.line] || warning.line
         })
       )
 

test/emptycode.test.js

@@ -0,0 +1,46 @@
+const stylelint = require('stylelint')
+const path = require('path')
+
+const processor = path.join(__dirname, '../lib/index.js')
+const rules = {
+  'no-empty-source': true
+}
+
+describe('empty source', () => {
+  let data
+
+  beforeAll(done => {
+    stylelint
+      .lint({
+        code: '',
+        config: {
+          processors: [processor],
+          rules
+        }
+      })
+      .then(result => {
+        data = result
+        done()
+      })
+      .catch(err => {
+        data = err
+        done()
+      })
+  })
+
+  it('should have one result', () => {
+    expect(data.results.length).toEqual(1)
+  })
+
+  it('should have errored', () => {
+    expect(data.errored).toEqual(true)
+  })
+
+  it('should have one warning', () => {
+    expect(data.results[0].warnings.length).toEqual(1)
+  })
+
+  it('should have the right line number', () => {
+    expect(data.results[0].warnings[0].line).toEqual(1)
+  })
+})