Fix serialization of existing properties with floats as dtype (#375)

* fix serialization of existing properties with floats as dtype

* update changelog

Author: rschwanhold

Changelog.md

@@ -17,6 +17,7 @@ For upgrade instructions, please check the respective *Breaking Changes* section
 - Bump scipy to `1.6.0` and `scikit-image` to `0.18.0` while keeping `numpy` to under `1.20.0` [#372](https://github.com/scalableminds/webknossos-cuber/pull/372/files)
 
 ### Fixed
+- Fixes a bug where modifications to an existing dataset with floats as dtype failed. [#375](https://github.com/scalableminds/webknossos-cuber/pull/375)
 
 ## [0.8.6](https://github.com/scalableminds/webknossos-cuber/releases/tag/v0.8.6) - 2021-07-29
 [Commits](https://github.com/scalableminds/webknossos-cuber/compare/v0.8.5...v0.8.6)

wkcuber/api/properties/layer_properties.py

@@ -46,10 +46,10 @@ def _extract_num_channels(
 
 
 properties_floating_type_to_python_type = {
-    "float": np.dtype("float32"),
-    np.float: np.dtype("float32"),
-    float: np.dtype("float32"),
-    "double": np.dtype("float64"),
+    "float": "float32",
+    np.float: "float32",
+    float: "float32",
+    "double": "float64",
 }
 
 python_floating_type_to_properties_type = {