Added an error check for charset conversion result for mail folder creation,

patch by mkaply@us.ibm.com,
bug 156336, r=naving, sr=bienvenu.

mailnews/base/resources/locale/en-US/messenger.properties

@@ -64,6 +64,7 @@ downloadingMail=Downloading Mail for Offline Use
 sendingUnsent=Sending Unsent Messages
 
 folderExists=A folder with that name already exists. Please enter a different name.
+folderCreationFailed=The folder could not be created because the folder name you specified contains an unrecognized character. Please enter a different name and try again.
 compactingFolder=Compacting folder %S...
 autoCompactAllFolders=Do you wish to compact all local and offline folders to save disk space?
 confirmFolderDeletionForFilter=Deleting the folder '%S' will disable its associated filter(s). Are you sure you want to delete the folder?

mailnews/local/src/nsLocalMailFolder.cpp

@@ -818,8 +818,13 @@ nsMsgLocalMailFolder::CreateSubfolder(const PRUnichar *folderName, nsIMsgWindow
      return rv;
 
   nsXPIDLCString nativeFolderName;
-  ConvertFromUnicode(nsMsgI18NFileSystemCharset(), nsAutoString(folderName),
+  rv = ConvertFromUnicode(nsMsgI18NFileSystemCharset(), nsAutoString(folderName),
                      getter_Copies(nativeFolderName));
+  if (NS_FAILED(rv) || (nativeFolderName.Length() == 0)) {
+     ThrowAlertMsg("folderCreationFailed", msgWindow);
+     // I'm returning this value so the dialog stays up
+     return NS_MSG_FOLDER_EXISTS;
+  }
   
   nsCAutoString safeFolderName;
   safeFolderName.Assign(nativeFolderName.get());