repair label for scalar multicurve plot

Wrap/Python/ba_plot.py

@@ -544,7 +544,8 @@ def plot_multicurve(results, xlabel, ylabel):
 
 def plot_multicurve_specular(results):
     plt.yscale('log')
-    plot_multicurve(results, r'$\alpha_{\rm i} \;(^\circ)$', r'Intensity')
+    xlabel = get_axes_labels(results[0], ba.Coords_UNDEFINED)[0]
+    plot_multicurve(results, xlabel, r'Intensity')
 
 #  **************************************************************************  #
 #  global settings