Cannot update DeviceSettings
## Observed behavior
Reported by @nucleogenesis [in the alpha13 bug bash ](https://www.notion.so/learningequality/Cannot-update-DeviceSettings-24859b98d15b411a8c55b83cddebc6d6?pvs=4)

> I tried to change a device setting, but it failed due to (it seems) a bad or unexpected value for secondary_storage_... 


## Context
0.16.0-a13

diff --git a/kolibri/utils/filesystem.py b/kolibri/utils/filesystem.py
index 59e9215f1f..7d19e43c1f 100644
--- a/kolibri/utils/filesystem.py
+++ b/kolibri/utils/filesystem.py
@@ -36,6 +36,9 @@ def resolve_path(path):
     :param path: Path to expand and resolve
     :return: The resolved path.
     """
+    if not path:  # Check if the path is empty
+        return path
+
     try:
         return os.path.realpath(os.path.expanduser(path))
     except (IOError, OSError):
['kolibri/utils/filesystem.py']