Use Strict Null Checks In TS Extension (#16244)

* Use Strict Null Checks In TS Extension

Updates the Ts extension to use strict null checks.

* Throw instead of returning undefined in some linkedmap cases

* fix small null check in buffersync

* Fix for request item null

extensions/typescript/tsconfig.json

@@ -6,7 +6,8 @@
 			"es5",
 			"es2015.promise"
 		],
-		"outDir": "./out"
+		"outDir": "./out",
+		"strictNullChecks": true
 	},
 	"exclude": [
 		"node_modules",