[FE 1.0] Don't use identifier in WhenMissingCase.kt if it wasn't provided

^KT-49702 Fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java

@@ -32555,6 +32555,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                 runTest("compiler/testData/diagnostics/tests/when/kt48653_before.kt");
             }
 
+            @Test
+            @TestMetadata("kt49702.kt")
+            public void testKt49702() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/when/kt49702.kt");
+            }
+
             @Test
             @TestMetadata("kt9929.kt")
             public void testKt9929() throws Exception {