Fix parsing of ESLint reports in jest-junit format

The [ESLint junit formatter](https://www.npmjs.com/package/eslint-junit)
does not include a total time attribute for the root `<testsuites>`
element.

src/parsers/jest-junit/jest-junit-parser.ts

@@ -43,7 +43,7 @@ export class JestJunitParser implements TestParser {
             return sr
           })
 
-    const time = parseFloat(junit.testsuites.$.time) * 1000
+    const time = junit.testsuites.$ && parseFloat(junit.testsuites.$.time) * 1000
     return new TestRunResult(path, suites, time)
   }