Minor, add regression test on incomplete code with callable reference

#KT-13685 Fixed

(cherry picked from commit c8b30d3310c990193414d7f82bedd50189e0109c)

compiler/testData/diagnostics/tests/regressions/kt13685.kt

@@ -0,0 +1,6 @@
+// !DIAGNOSTICS: -UNREACHABLE_CODE
+
+fun foo() {
+    val <!UNUSED_VARIABLE!>text<!>: List<Any> = null!!
+    text.<!UNRESOLVED_REFERENCE!>map<!> <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>Any<!><!SYNTAX!>?<!>::<!UNRESOLVED_REFERENCE!>toString<!>
+}

compiler/testData/diagnostics/tests/regressions/kt13685.txt

@@ -0,0 +1,3 @@
+package
+
+public fun foo(): kotlin.Unit