Move: Fix exception on moving Kotlin file without declarations

#KT-14114 Fixed

idea/src/org/jetbrains/kotlin/idea/refactoring/move/moveDeclarations/MoveKotlinDeclarationsProcessor.kt

@@ -130,6 +130,8 @@ class MoveKotlinDeclarationsProcessor(
     fun getConflictsAsUsages(): List<UsageInfo> = conflicts.entrySet().map { ConflictUsageInfo(it.key, it.value) }
 
     public override fun findUsages(): Array<UsageInfo> {
+        if (elementsToMove.isEmpty()) return UsageInfo.EMPTY_ARRAY
+
         val newContainerName = descriptor.moveTarget.targetContainerFqName?.asString() ?: ""
 
         fun collectUsages(kotlinToLightElements: Map<KtNamedDeclaration, List<PsiNamedElement>>, result: MutableList<UsageInfo>) {

idea/testData/refactoring/move/kotlin/moveFile/moveFileWithoutDeclarations/after/q/test.kt

@@ -0,0 +1 @@
+package q

idea/testData/refactoring/move/kotlin/moveFile/moveFileWithoutDeclarations/before/p/test.kt

@@ -0,0 +1 @@
+package p

idea/testData/refactoring/move/kotlin/moveFile/moveFileWithoutDeclarations/moveFileWithoutDeclarations.test

@@ -0,0 +1,5 @@
+{
+  "mainFile": "p/test.kt",
+  "type": "MOVE_FILES",
+  "targetPackage": "q"
+}

idea/tests/org/jetbrains/kotlin/idea/refactoring/move/MoveTestGenerated.java

@@ -257,6 +257,12 @@ public class MoveTestGenerated extends AbstractMoveTest {
         doTest(fileName);
     }
 
+    @TestMetadata("kotlin/moveFile/moveFileWithoutDeclarations/moveFileWithoutDeclarations.test")
+    public void testKotlin_moveFile_moveFileWithoutDeclarations_MoveFileWithoutDeclarations() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/move/kotlin/moveFile/moveFileWithoutDeclarations/moveFileWithoutDeclarations.test");
+        doTest(fileName);
+    }
+
     @TestMetadata("kotlin/moveFile/moveFileWithoutPackageRename/moveFileWithoutPackageRename.test")
     public void testKotlin_moveFile_moveFileWithoutPackageRename_MoveFileWithoutPackageRename() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/move/kotlin/moveFile/moveFileWithoutPackageRename/moveFileWithoutPackageRename.test");