Fix KNPE in "Move member to companion" for expect class #KT-28383 Fixed

idea/testData/intentions/moveToCompanion/expectClass.kt

@@ -0,0 +1,5 @@
+// ERROR: The feature "multi platform projects" is experimental and should be enabled explicitly
+
+expect class Some {
+    val <caret>x: Int
+}

idea/testData/intentions/moveToCompanion/expectClass.kt.after

@@ -0,0 +1,7 @@
+// ERROR: The feature "multi platform projects" is experimental and should be enabled explicitly
+
+expect class Some {
+    companion object {
+        val x: Int
+    }
+}