[bugfix] Fix broken run_detector for non-change detectors

The HTTP API for running detectors accept only a "raster_id" POST field
for non-change detectors, but our Python library was sending also a
"secondary_raster_id" with a None value, resulting in a server error.

This fixes it.

src/picterra/client.py

@@ -754,9 +754,12 @@ def run_detector(
             operation_id: The id of the operation. You typically want to pass this
                 to `download_result_to_feature_collection`
         """
+        body = {"raster_id": raster_id}
+        if secondary_raster_id is not None:
+            body["secondary_raster_id"] = secondary_raster_id
         resp = self.sess.post(
             self._api_url("detectors/%s/run/" % detector_id),
-            json={"raster_id": raster_id, "secondary_raster_id": secondary_raster_id},
+            json=body,
         )
         if not resp.ok:
             raise APIError(resp.text)

tests/test_client.py

@@ -387,12 +387,12 @@ def add_mock_remote_import_responses(upload_id, post_body):
 
 
 def add_mock_detector_run_responses(detector_id, raster_id, secondary_raster_id=None):
+    data = {"raster_id": raster_id}
+    if secondary_raster_id:
+        data["secondary_raster_id"] = secondary_raster_id
     _add_api_response(
         "detectors/%s/run/" % detector_id, responses.POST, OP_RESP,
-        match=responses.matchers.json_params_matcher({
-            "raster_id": raster_id,
-            "secondary_raster_id": secondary_raster_id,
-        }),
+        match=responses.matchers.json_params_matcher(data),
     )
     # First status check
     data = {"status": "running"}