Correctly remove stale .error.txt baselines

Author: RyanCavanaugh

src/harness/compilerRunner.ts

@@ -136,9 +136,7 @@ class CompilerBaselineRunner extends RunnerBase {
 
             // check errors
             it("Correct errors for " + fileName, () => {
-                if (this.errors) {
-                    Harness.Compiler.doErrorBaseline(justName, toBeCompiled.concat(otherFiles), result.errors);
-                }
+                 Harness.Compiler.doErrorBaseline(justName, toBeCompiled.concat(otherFiles), result.errors);
             });
 
             it (`Correct module resolution tracing for ${fileName}`, () => {

src/harness/harness.ts

@@ -1407,7 +1407,7 @@ namespace Harness {
 
         export function doErrorBaseline(baselinePath: string, inputFiles: TestFile[], errors: ts.Diagnostic[]) {
             Harness.Baseline.runBaseline(baselinePath.replace(/\.tsx?$/, ".errors.txt"), (): string => {
-                if (errors.length === 0) {
+                if (!errors || (errors.length === 0)) {
                     /* tslint:disable:no-null-keyword */
                     return null;
                     /* tslint:enable:no-null-keyword */