Fix various linter errors

src/tasks.js

@@ -194,7 +194,7 @@ async function startTask(id, options) {
     assert.ok(sudoError, 'sudo should have errored because task did not complete!');
 
     // taskworker.sh forwards the exit code of the actual worker. It's either a raw signal number OR the exit code
-    let taskError = null;
+    let taskError;
     if (sudoError.timedOut) taskError = { message: `Task ${id} timed out`, code: ETIMEOUT };
     else if (sudoError.code === 70) taskError = { message: `Task ${id} stopped`, code: ESTOPPED }; // set by taskworker SIGTERM
     else if (sudoError.code === 9 /* SIGKILL */) taskError = { message: `Task ${id} ran out of memory or terminated`, code: ECRASHED }; // SIGTERM with oom gets set as 2 by nodejs