Fix initialization order in REPL

#KT-6843 Fixed

compiler/testData/repl/regressions/kt6843.repl

@@ -0,0 +1,5 @@
+>>> [data] class Person(val name: String)
+>>> var x: String? = "hello"
+>>> val y = x?.let { Person(it) }
+>>> y
+Person(name=hello)

compiler/testData/repl/simpleTwoVals.repl

@@ -0,0 +1,4 @@
+>>> val x = ""
+>>> val y = x
+>>> x == y
+true