do not assume pointers are populated

src/grung/types.py

@@ -112,9 +112,10 @@ class Pointer(Field):
         return ""
 
     def deserialize(self, value: str, db: TinyDB, recurse=True) -> value_type:
-        pt, puid = value.split("::")
-        if puid:
-            return db.table(pt).search(where("uid") == puid, recurse=recurse)[0]
+        if value:
+            pt, puid = value.split("::")
+            if puid:
+                return db.table(pt).search(where("uid") == puid, recurse=recurse)[0]
         return value