Fix SAM conversion when lambda is the last expression of another lambda

#KT-39691 Fixed

compiler/testData/diagnostics/tests/samConversions/conversionOnLambdaAsLastExpression.kt

@@ -0,0 +1,20 @@
+// FIR_IDENTICAL
+
+// FILE: C.java
+
+public interface C { void on(String s); }
+
+// FILE: A.java
+
+public class A { void add(C c) {} }
+
+// FILE: test.kt
+
+class B : A() {
+    fun test(x: Any?) {
+        add(foo { { _ : String -> Unit } })
+        add(x?.let { { _ : String -> Unit } })
+    }
+}
+
+fun <T> foo(f: () -> T): T = f()