[FIR] Fix cfg crash with multiple postponed arguments

compiler/fir/analysis-tests/testData/resolveWithStdlib/complexPostponedCfg.kt

@@ -0,0 +1,20 @@
+// !DUMP_CFG
+
+interface FirBase
+interface FirFunctionCall : FirBase
+
+
+fun foo(statements: List<FirBase>, arguments: List<FirBase>, explicitReceiver: FirBase): List<FirFunctionCall> {
+
+    val firstCalls = with(statements.last() as FirFunctionCall) setCall@{
+        buildList {
+            add(this@setCall)
+            with(arguments.last() as FirFunctionCall) plusCall@{
+                add(this@plusCall)
+                add(explicitReceiver as FirFunctionCall)
+            }
+        }
+    }
+
+    return firstCalls
+}