LL API: fix kt -> fir mapping of type inside nullable type

idea/idea-frontend-fir/idea-fir-low-level-api/src/org/jetbrains/kotlin/idea/fir/low/level/api/element/builder/FirElementBuilder.kt

@@ -50,6 +50,7 @@ internal class FirElementBuilder {
             }
             deparenthesized is KtObjectLiteralExpression -> deparenthesized.objectDeclaration
             deparenthesized is KtStringTemplateEntryWithExpression -> deparenthesized.expression
+            deparenthesized is KtUserType && deparenthesized.parent is KtNullableType -> deparenthesized.parent as KtNullableType
             else -> deparenthesized
         }
     }

idea/idea-frontend-fir/idea-fir-low-level-api/testdata/getOrBuildFir/types/nullableTypeWithooutQuestionMark.kt

@@ -0,0 +1,2 @@
+
+fun x(): <expr>Int</expr>? = TODO()

idea/idea-frontend-fir/idea-fir-low-level-api/testdata/getOrBuildFir/types/nullableTypeWithooutQuestionMark.txt

@@ -0,0 +1,5 @@
+KT element: KtUserType
+FIR element: FirResolvedTypeRefImpl
+
+FIR element rendered:
+R|kotlin/Int?|

idea/idea-frontend-fir/idea-fir-low-level-api/tests/org/jetbrains/kotlin/idea/fir/low/level/api/GetOrBuildFirTestGenerated.java

@@ -475,6 +475,12 @@ public class GetOrBuildFirTestGenerated extends AbstractGetOrBuildFirTest {
             runTest("idea/idea-frontend-fir/idea-fir-low-level-api/testdata/getOrBuildFir/types/nestedTypeArgument.kt");
         }
 
+        @Test
+        @TestMetadata("nullableTypeWithooutQuestionMark.kt")
+        public void testNullableTypeWithooutQuestionMark() throws Exception {
+            runTest("idea/idea-frontend-fir/idea-fir-low-level-api/testdata/getOrBuildFir/types/nullableTypeWithooutQuestionMark.kt");
+        }
+
         @Test
         @TestMetadata("typeArgument.kt")
         public void testTypeArgument() throws Exception {