fix errors when overwriting existing file

Author: vkovec

Assets/FbxExporters/Editor/ConvertToPrefabEditorWindow.cs

@@ -53,11 +53,13 @@ protected override void Export ()
                 var prefabPath = System.IO.Path.Combine (prefabDirPath, m_prefabFileName + ".prefab");
 
                 // check if file already exists, give a warning if it does
-                CheckFileExists (fbxPath);
-                CheckFileExists (prefabPath);
+                if (!OverwriteExistingFile (fbxPath) || !OverwriteExistingFile (prefabPath)) {
+                    return;
+                }
 
                 if (m_toConvert == null) {
                     Debug.LogError ("FbxExporter: missing object for conversion");
+                    return;
                 }
 
                 if (m_toConvert.Length == 1) {

Assets/FbxExporters/Editor/ExportModelEditorWindow.cs

@@ -238,21 +238,26 @@ protected void OnGUI ()
                 }
             }
 
-            protected void CheckFileExists(string filePath){
+            /// <summary>
+            /// Checks whether the file exists and if it does then asks if it should be overwritten.
+            /// </summary>
+            /// <returns><c>true</c>, if file should be overwritten, <c>false</c> otherwise.</returns>
+            /// <param name="filePath">File path.</param>
+            protected bool OverwriteExistingFile(string filePath){
                 // check if file already exists, give a warning if it does
                 if (System.IO.File.Exists (filePath)) {
                     bool overwrite = UnityEditor.EditorUtility.DisplayDialog (
                         string.Format("{0} Warning", ModelExporter.PACKAGE_UI_NAME), 
                         string.Format("File {0} already exists.", filePath), 
                         "Overwrite", "Cancel");
                     if (!overwrite) {
-                        this.Close ();
-
                         if (GUI.changed) {
                             SaveExportSettings ();
                         }
+                        return false;
                     }
                 }
+                return true;
             }
         }
 
@@ -285,7 +290,9 @@ protected override void Export(){
 
                 filePath = System.IO.Path.Combine (filePath, m_exportFileName + ".fbx");
 
-                CheckFileExists (filePath);
+                if (!OverwriteExistingFile (filePath)) {
+                    return;
+                }
 
                 if (ModelExporter.ExportObjects (filePath, exportType: m_animExportType, lodExportType: ExportSettings.GetLODExportType()) != null) {
                     // refresh the asset database so that the file appears in the