diff --git a/src/Grafoscopio/FileUtils.class.st b/src/Grafoscopio/FileUtils.class.st
new file mode 100644
index 0000000..411aa0d
--- /dev/null
+++ b/src/Grafoscopio/FileUtils.class.st
@@ -0,0 +1,28 @@
+"
+I provide some convenience functionality to work with files.
+"
+Class {
+	#name : #FileUtils,
+	#superclass : #Object,
+	#category : #'Grafoscopio-Model'
+}
+
+{ #category : #utilities }
+FileUtils class >> createFilesNamed: fileNames endingWith: fileExtension intoFolder: aFolder [
+	
+	| createdFiles fullFileName existingFiles typedFileName |
+	createdFiles := OrderedCollection new.
+	existingFiles := OrderedCollection new.
+	fileNames do: [ :eachFile | 
+		typedFileName := eachFile, fileExtension.
+		fullFileName := aFolder / typedFileName.
+		fullFileName exists
+			ifFalse: [ 
+				fullFileName ensureCreateFile.
+				createdFiles add: fullFileName basename ]
+			ifTrue: [existingFiles add: fullFileName basename ]].
+	^ (Dictionary new  
+			at: 'created files' put: createdFiles;
+			at: 'existing files' put: existingFiles;
+			yourself)
+]
diff --git a/src/Grafoscopio/GrafoscopioNode.class.st b/src/Grafoscopio/GrafoscopioNode.class.st
index 8d7d3be..b56d998 100644
--- a/src/Grafoscopio/GrafoscopioNode.class.st
+++ b/src/Grafoscopio/GrafoscopioNode.class.st
@@ -41,7 +41,7 @@ GrafoscopioNode class >> cleanTreeRootReferences [
 	clipboard preorderTraversal allButFirstDo: [ :n |
 			ref := n.
 			n level - 1 timesRepeat: [ ref := ref parent ].
-			ref parent: nil 
+			ref ifNotNil: [ ref parent: nil ] 
 	] 
 ]
 
diff --git a/src/Grafoscopio/ManifestGrafoscopio.class.st b/src/Grafoscopio/ManifestGrafoscopio.class.st
index 3dd416b..f578248 100644
--- a/src/Grafoscopio/ManifestGrafoscopio.class.st
+++ b/src/Grafoscopio/ManifestGrafoscopio.class.st
@@ -26,3 +26,8 @@ ManifestGrafoscopio class >> ruleRBLongMethodsRuleV1FalsePositive [
 ManifestGrafoscopio class >> ruleRBSentNotImplementedRuleV1FalsePositive [
 	^ #(#(#(#RGMetaclassDefinition #(#'GrafoscopioGUI class' #GrafoscopioGUI)) #'2015-12-23T10:38:16.706667-05:00') #(#(#RGClassDefinition #(#GrafoscopioGUI)) #'2016-01-06T18:53:45.844051-05:00') #(#(#RGMethodDefinition #(#GrafoscopioNotebook #newWindowMainMenu #false)) #'2016-12-17T18:51:40.617924-05:00') )
 ]
+
+{ #category : #'code-critics' }
+ManifestGrafoscopio class >> ruleRBStringConcatenationRuleV1FalsePositive [
+	^ #(#(#(#RGMethodDefinition #(#'FileUtils class' #createFilesNamed:endingWith:intoFolder: #true)) #'2017-01-01T21:48:26.712639-05:00') )
+]