PSI: Do not delete package directive for file in default package

#KT-24968 Fixed

compiler/psi/src/org/jetbrains/kotlin/psi/KtPackageDirective.java

@@ -119,7 +119,10 @@ public class KtPackageDirective extends KtModifierListOwnerStub<KotlinPlaceHolde
 
     public void setFqName(@NotNull FqName fqName) {
         if (fqName.isRoot()) {
-            delete();
+            if (!getFqName().isRoot()) {
+                //noinspection ConstantConditions
+                replace(new KtPsiFactory(getProject()).createFile("").getPackageDirective());
+            }
             return;
         }
 

idea/testData/refactoring/copy/copyFileFromDefaultPackageToDefaultPackage/after/test.kt

@@ -0,0 +1,6 @@
+val a = 42
+
+// comment
+
+// some other comment
+val s = ""

idea/testData/refactoring/copy/copyFileFromDefaultPackageToDefaultPackage/after/test2.kt

@@ -0,0 +1,6 @@
+val a = 42
+
+// comment
+
+// some other comment
+val s = ""

idea/testData/refactoring/copy/copyFileFromDefaultPackageToDefaultPackage/before/test.kt

@@ -0,0 +1,6 @@
+val a = 42
+
+// comment
+
+// some other comment
+val s = ""

idea/testData/refactoring/copy/copyFileFromDefaultPackageToDefaultPackage/copyFIleToDefaultPackage.test

@@ -0,0 +1,5 @@
+{
+  "mainFile": "test.kt",
+  "targetPackage": "",
+  "newName": "test2.kt"
+}

idea/tests/org/jetbrains/kotlin/idea/refactoring/copy/CopyTestGenerated.java

@@ -64,6 +64,11 @@ public class CopyTestGenerated extends AbstractCopyTest {
         runTest("idea/testData/refactoring/copy/copyFIleFromDefaultPackage/copyFIleFromDefaultPackage.test");
     }
 
+    @TestMetadata("copyFileFromDefaultPackageToDefaultPackage/copyFIleToDefaultPackage.test")
+    public void testCopyFileFromDefaultPackageToDefaultPackage_CopyFIleToDefaultPackage() throws Exception {
+        runTest("idea/testData/refactoring/copy/copyFileFromDefaultPackageToDefaultPackage/copyFIleToDefaultPackage.test");
+    }
+
     @TestMetadata("copyFIleRetainContent/copyFIleRetainContent.test")
     public void testCopyFIleRetainContent_CopyFIleRetainContent() throws Exception {
         runTest("idea/testData/refactoring/copy/copyFIleRetainContent/copyFIleRetainContent.test");