[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/resolve/nestedCalls/kt5971NestedSafeCall.fir.kt

@@ -0,0 +1,9 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+//KT-5971 Missing error when fun argument is safe call
+
+fun foo(i: Int) {}
+
+fun test(s: String?) {
+    foo(s?.length)
+}