Update field type in NodeConfigurator
diff --git a/compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt b/compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt
index ddcdb7a..7e6409a 100644
--- a/compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt
+++ b/compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt
@@ -466,7 +466,7 @@
             +fieldList(import).withTransform()
             +declarations.withTransform()
             +stringField("name")
-            +field("sourceFile", sourceFileType, nullable = true)
+            +field("sourceFile", sourceFileType, nullable = false)
             +field("sourceFileLinesMapping", sourceFileLinesMappingType, nullable = true)
             +symbol("FirFileSymbol")
         }