Skip samples with no wind speed/direction in hodographs

lib/xmet/hodograph.py

@@ -168,6 +168,9 @@ class Hodograph():
 
     def each_significant_sample(self, sounding: Sounding):
         for sample in sounding.hodograph_samples():
+            if sample.wind_speed is None or sample.wind_dir is None:
+                continue
+
             if self.color(sample.height) is None:
                 break