Omit unit on y axis if it is None

nnfwtbn/plot.py

@@ -237,10 +237,14 @@ def hist(dataframe, variable, bins, stacks, selection=None,
         axes.set_xlabel(variable.name, horizontalalignment='right', x=0.95)
 
     if equidistant_bins:
-        axes.set_ylabel("Events / %g %s" % (bins[1] - bins[0], variable.unit),
-                        horizontalalignment='right', y=0.95)
+        if variable.unit is not None:
+            axes.set_ylabel("Events / %g %s" % (bins[1] - bins[0], variable.unit),
+                            horizontalalignment='right', y=0.95)
+        else:
+            axes.set_ylabel("Events / %g" % (bins[1] - bins[0]),
+                            horizontalalignment='right', y=0.95)
     else:
-        axes.set_ylabel("Events / bin", horizontalalignment='right', y=0.95)
+        axes.set_ylabel("Events / Bin", horizontalalignment='right', y=0.95)