FIR: Fix safe call receiver nullability after null check

compiler/testData/diagnostics/tests/j+k/safeCallDefinitelyNotNull.kt

@@ -0,0 +1,11 @@
+// SKIP_TXT
+// FILE: Api.java
+import org.jetbrains.annotations.NotNull;
+public abstract class Api<T> {
+    public abstract void typeOf(@NotNull T node);
+}
+
+// FILE: main.kt
+fun <E> foo(a: Api<E>, e: E?) {
+    e?.let { a.typeOf(<!DEBUG_INFO_SMARTCAST!>e<!>) }
+}