Add test for outdated smart cast with elvis issue

#KT-5335 Obsolete

compiler/testData/diagnostics/tests/smartCasts/elvisNothingRHS.kt

@@ -0,0 +1,11 @@
+class C {
+    fun foo() {}
+}
+
+fun test(a: C?, nn: () -> Nothing?) {
+    a ?: nn()
+    a<!UNSAFE_CALL!>.<!>foo()
+
+    a ?: return
+    <!DEBUG_INFO_SMARTCAST!>a<!>.foo()
+}