refactor(server): Fix dead branch in addCustomMiddleware

The early-return check `!projectCustomMiddleware.length === 0` parses as
`(!length) === 0`, which is always false for both empty and non-empty
arrays. The branch never fired, but the for-loop below already handles
empty arrays as a no-op, so behavior was unchanged.

Initially found by @EdrilanBerisha in
#1391

Author: RandomByte

packages/server/lib/middleware/MiddlewareManager.js

@@ -245,7 +245,7 @@ class MiddlewareManager {
 	async addCustomMiddleware() {
 		const project = this.graph.getRoot();
 		const projectCustomMiddleware = project.getCustomMiddleware();
-		if (!projectCustomMiddleware.length === 0) {
+		if (projectCustomMiddleware.length === 0) {
 			return; // No custom middleware defined
 		}