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

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifiesInLoop.fir.kt

@@ -0,0 +1,10 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+fun foo(arg: Int?) {
+    run {
+        var x = arg
+        while (x != null) {
+            x = x.hashCode()
+            if (x == 0) x = null
+        }
+    }
+}