prevent too fast map_to_image calls (returns None)

helpers/functional.py

@@ -68,9 +68,12 @@ def cell2row(grid_string, meta_df, return_row = False):
 
 def map_to_image(map, return_centre=False, return_gridcell=False, l2a=True):
 
-    # 1. get bounds
-    bbox = map.get_bbox()
-    center = [(bbox[3]+bbox[1])/2, (bbox[2]+bbox[0])/2]
+    try:
+        # 1. get bounds
+        bbox = map.get_bbox()
+        center = [(bbox[3]+bbox[1])/2, (bbox[2]+bbox[0])/2]
+    except:
+        return None
 
     # 2. translate coordinate to major-tom tile
     rows, cols = grid.latlon2rowcol([center[0]], [center[1]])