Move: Fix exception on moving Kotlin file without declarations

#KT-14114 Fixed

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"
+}