[FIR] Make UNSAFE_INFIX_CALL and UNSAFE_OPERATOR_CALL parameter nullable

This fixes an NPE in the IDE in presence of a syntax error when the
argument expression has no source.

#KT-64062 Fixed

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -26348,6 +26348,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/nullableTypes/takingNullabilityFromExplicitTypeArgmentsInsteadOfUsingFlexibleTypes.kt");
             }
 
+            @Test
+            @TestMetadata("unsafeCallOnOperatorRedCode.kt")
+            public void testUnsafeCallOnOperatorRedCode() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/nullableTypes/unsafeCallOnOperatorRedCode.kt");
+            }
+
             @Test
             @TestMetadata("uselessElvis.kt")
             public void testUselessElvis() throws Exception {