Fix initialization for time is None

Author: fluidnumericsJoe

parcels/particleset.py

@@ -102,6 +102,7 @@ def __init__(
 
         lon = np.empty(shape=0) if lon is None else convert_to_flat_array(lon)
         lat = np.empty(shape=0) if lat is None else convert_to_flat_array(lat)
+        time = np.empty(shape=0) if time is None else convert_to_flat_array(time)
 
         if isinstance(pid_orig, (type(None), bool)):
             pid_orig = np.arange(lon.size)
@@ -116,22 +117,22 @@ def __init__(
             depth = convert_to_flat_array(depth)
         assert lon.size == lat.size and lon.size == depth.size, "lon, lat, depth don't all have the same lenghts"
 
-        if time is not None:
-            time = convert_to_flat_array(time)
+        if time.size > 0:
             time = np.repeat(time, lon.size) if time.size == 1 else time
 
-            if time.size > 0 and type(time[0]) in [np.datetime64, np.timedelta64]:
+            if type(time[0]) in [np.datetime64, np.timedelta64]:
                 pass  # already in the right format
-            elif time.size > 0 and type(time[0]) in [datetime, date]:
+            elif type(time[0]) in [datetime, date]:
                 time = np.array([np.datetime64(t) for t in time])
-            elif time.size > 0 and type(time[0]) in [timedelta]:
+            elif type(time[0]) in [timedelta]:
                 time = np.array([np.timedelta64(t) for t in time])
             else:
                 raise NotImplementedError("particle time must be a datetime, timedelta, or date object")
 
             time = np.array([self.time_origin.reltime(t) if _convert_to_reltime(t) else t for t in time])
 
-        assert lon.size == time.size, "time and positions (lon, lat, depth) do not have the same lengths."
+            assert lon.size == time.size, "time and positions (lon, lat, depth) do not have the same lengths."
+
         if fieldset.time_interval:
             _warn_particle_times_outside_fieldset_time_bounds(time, fieldset.time_interval)