fix(tsc): initialize extensionsChangedException correctly in run function

Author: johnsoncodehk

packages/tsc/index.ts

@@ -6,8 +6,8 @@ const windowsPathReg = /\\/g;
 export function run(tscPath = require.resolve('typescript/lib/tsc')) {
 
 	let runExtensions = ['.vue'];
+	let extensionsChangedException: Error | undefined;
 
-	const extensionsChangedException = new Error('extensions changed');
 	const main = () => runTsc(
 		tscPath,
 		runExtensions,
@@ -31,7 +31,7 @@ export function run(tscPath = require.resolve('typescript/lib/tsc')) {
 			}
 			else {
 				runExtensions = allExtensions;
-				throw extensionsChangedException;
+				throw extensionsChangedException = new Error('extensions changed');
 			}
 		}
 	);