reduce calls to getter

lib/Compilation.js

@@ -1149,10 +1149,11 @@ BREAKING CHANGE: Asset processing hooks in Compilation has been merged into a si
 				// Here webpack is using heuristic that assumes
 				// mostly esm dependencies would be used
 				// so we don't allocate extra string for them
+				const category = dep.category;
 				const cacheKey =
-					dep.category === esmDependencyCategory
+					category === esmDependencyCategory
 						? resourceIdent
-						: `${dep.category}${resourceIdent}`;
+						: `${category}${resourceIdent}`;
 				const constructor = dep.constructor;
 				let innerMap;
 				let factory;