Don't crash when not able to read maximum file name length

Just use a safe-ish maximum then.

Fixes Sentry issue CURA-1QY.

cura/Settings/MachineNameValidator.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2016 Ultimaker B.V.
+# Copyright (c) 2021 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 from PyQt5.QtCore import pyqtSlot, pyqtProperty, QObject, pyqtSignal, QRegExp
@@ -23,7 +23,7 @@ class MachineNameValidator(QObject):
         #Compute the validation regex for printer names. This is limited by the maximum file name length.
         try:
             filename_max_length = os.statvfs(Resources.getDataStoragePath()).f_namemax
-        except AttributeError: #Doesn't support statvfs. Probably because it's not a Unix system.
+        except (AttributeError, EnvironmentError):  # Doesn't support statvfs. Probably because it's not a Unix system. Or perhaps there is no permission or it doesn't exist.
             filename_max_length = 255 #Assume it's Windows on NTFS.
         machine_name_max_length = filename_max_length - len("_current_settings.") - len(ContainerRegistry.getMimeTypeForContainer(InstanceContainer).preferredSuffix)
         # Characters that urllib.parse.quote_plus escapes count for 12! So now