Use initial system for completion if common one is effectively empty

Otherwise we can get unsubstituted type variables as expected types and
 then write wrong information for assertions

 #KT-41470 Fixed

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -13877,6 +13877,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/inference/manyFlexibleTypeParametersFromJavaAndConversions.kt");
         }
 
+        @TestMetadata("mapCollectChainWithNullResult.kt")
+        public void testMapCollectChainWithNullResult() throws Exception {
+            runTest("compiler/testData/codegen/box/inference/mapCollectChainWithNullResult.kt");
+        }
+
         @TestMetadata("noCoercionToUniForNullableLambdaReturnType.kt")
         public void testNoCoercionToUniForNullableLambdaReturnType() throws Exception {
             runTest("compiler/testData/codegen/box/inference/noCoercionToUniForNullableLambdaReturnType.kt");