[web] [build] stricter guards for printTestBundleSize

web/build.gradle.kts

@@ -35,6 +35,7 @@ subprojects {
         }
     }
 
+    pluginManager.withPlugin("kotlin-multiplatform") {
         val printTestBundleSize by tasks.registering {
             doLast {
                 val bundlePath = buildDir.resolve(
@@ -50,6 +51,8 @@ subprojects {
         afterEvaluate {
             tasks.named("jsTest") { finalizedBy(printTestBundleSize) }
         }
+    }
+
 
     if (isSampleProject()) {
         val printBundleSize by tasks.registering {