Avoid building stubs in KtFile::getClasses for compiled files

In Gradle, JavaPsiFacade finds Kotlin compiled files as KtFile instances
and tries to obtain classes from them.

And while it returns an empty array anyway, it starts building
unnecessary stub when calling `isScript`

idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/IDELightClassGenerationSupport.kt

@@ -342,8 +342,9 @@ class IDELightClassGenerationSupport(private val project: Project) : LightClassG
 
 class KtFileClassProviderImpl(val lightClassGenerationSupport: LightClassGenerationSupport) : KtFileClassProvider {
     override fun getFileClasses(file: KtFile): Array<PsiClass> {
-        if (file.isCompiled) {
-            return arrayOf()
+        // TODO We don't currently support finding light classes for scripts
+        if (file.isCompiled || file.isScript()) {
+            return PsiClass.EMPTY_ARRAY
         }
 
         val result = arrayListOf<PsiClass>()