fix failing pytest

Author: Sean Sullivan

elastic_datashader/elastic.py

@@ -206,7 +206,7 @@ def get_search_base(
         base_s = base_s.filter("range", **time_range)
 
     #filter the ellipse search range in the data base query so the legen matches the tiles
-    if params['render_mode'] =="ellipses":
+    if params.get('render_mode',"") =="ellipses":
         units = convert_nm_to_ellipse_units(params['search_nautical_miles'],params['ellipse_units'])
         search_range = {params["ellipse_major"]:{"lte":units}}
         base_s = base_s.filter("range",**search_range)

elastic_datashader/routers/legend.py

@@ -137,7 +137,7 @@ async def provide_legend(idx: str, field_name: str, request: Request):  # pylint
                 "lon": min(180.0, extent["maxLon"]),
             },
         }
-        if params['render_mode'] == "ellipses":
+        if params.get('render_mode',"") == "ellipses":
             #expand the bbox by half the search_nautical_miles or we cut off items on the edge
             #this still isn't 100% accurate because the tiles are squares and our viewport is rectangular
             #you can sometimes see a little tiny part of the ellipse and it isn't counted