Implement handling of unavailable biology image loops

Modified the biology image loop handling process to deal with cases where image
loops are not available. This is necessary due to the removal of the ciliates
variable, and the name change of the turbidity variable in V2021-11.

A new list, 'unavailable_loops' has been created to store image loops
that are not available. Those loops are then removed from a copy of the biology
loops data structure to produce the image loops data structure that is passed to
the page renderer.

salishsea_site/views/salishseacast.py

@@ -19,6 +19,7 @@
 
 """salishsea_site SalishSeaCast views
 """
+import copy
 import logging
 import os
 import urllib.parse
@@ -742,11 +743,14 @@ def nowcast_biology(request):
         ],
         "biology loops": [],
     }
+    unavailable_loops = []
     for image_loop in biology_image_loops.loops:
         images_available = image_loop.available("nowcast-green", results_date)
-        if images_available:
-            available_figures["biology loops"].append(images_available)
-            image_loop.hrs = image_loop.hours("nowcast-green", results_date)
+        if not images_available:
+            unavailable_loops.append(image_loop)
+            continue
+        available_figures["biology loops"].append(images_available)
+        image_loop.hrs = image_loop.hours("nowcast-green", results_date)
     if not any(available_figures["baynes sound"] + available_figures["biology loops"]):
         raise HTTPNotFound
     figure_links = (
@@ -757,13 +761,16 @@ def nowcast_biology(request):
         if available_figures["baynes sound"]
         else []
     )
+    image_loops = copy.deepcopy(biology_image_loops)
+    for image_loop in unavailable_loops:
+        image_loops.loops.remove(image_loop)
     return {
         "results_date": results_date,
         "run_type": "nowcast-green",
         "run_date": results_date,
         "figure_links": figure_links,
         "available_figures": available_figures,
-        "image_loops": biology_image_loops,
+        "image_loops": image_loops,
         "baynes_sound_figures": baynes_sound_figures,
     }