Fix for KT-10715: Verify error on incrementing backing field from accessor

compiler/testData/codegen/box/properties/kt10715.kt

@@ -0,0 +1,17 @@
+fun box(): String {
+    var a = Base()
+
+    val count = a.count
+    if (count != 0) return "fail 1: $count"
+
+    val count2 = a.count
+    if (count2 != 1) return "fail 2: $count2"
+
+    return "OK"
+
+}
+
+class Base {
+    var count: Int = 0
+        get() = field++
+}