fix(dependency-injection): adjust based on review

Fixes #171

Author: silbinarywolf

src/injection.js

@@ -8,13 +8,11 @@ export function autoinject(potentialTarget?: any): any {
   let deco = function(target) {
     if (!target.hasOwnProperty('inject')) {
       target.inject = (metadata.getOwn(metadata.paramTypes, target) || _emptyParameters).slice();
-      if (target.inject &&
-        target.inject.length > 0) {
-        // TypeScript 3.0 metadata for "...rest" gives type "Object"
-        // if last parameter is "Object", assume it's a ...rest and remove that metadata.
-        if (target.inject[target.inject.length - 1] === Object) {
-          target.inject.splice(-1,1);
-        }
+      // TypeScript 3.0 metadata for "...rest" gives type "Object"
+      // if last parameter is "Object", assume it's a ...rest and remove that metadata.
+      if (target.inject.length > 0 &&
+          target.inject[target.inject.length - 1] === Object) {
+        target.inject.pop();
       }
     }
   };