Fix for KT-6196: ClassCastException on unit property initializer

#KT-6196 Fixed

compiler/testData/codegen/box/unit/ifElse.kt

@@ -0,0 +1,31 @@
+class A (val p: String, p1: String, p2: String) {
+
+    var cond1: String = ""
+
+    var cond2: String = ""
+
+    val prop1 = if (cond1(p)) p1
+
+    val prop2 = if (cond2(p)) else;
+
+
+    fun cond1(p: String): Boolean {
+        cond1 = "cond1"
+        return p == "test"
+    }
+
+    fun cond2(p: String): Boolean {
+        cond2 = "cond2"
+        return p == "test"
+    }
+}
+
+fun box(): String {
+    val a = A("test", "OK", "fail")
+
+    if (a.cond1 != "cond1") return "fail 2 : ${a.cond1}"
+
+    if (a.cond2 != "cond2") return "fail 3 : ${a.cond2}"
+
+    return "OK"
+}