typo fixed

Author: delandmeterp

parcels/field.py

@@ -202,7 +202,7 @@ def __init__(self, name, data, lon=None, lat=None, depth=None, time=None, grid=N
         self.interp_method = interp_method
         self.fieldset = None
         if allow_time_extrapolation is None:
-            self.allow_time_extrapolation = True if len(self.grid.time) == 0 else False
+            self.allow_time_extrapolation = True if len(self.grid.time) == 1 else False
         else:
             self.allow_time_extrapolation = allow_time_extrapolation