Vis: Handle missing data more gracefully (#175)

If there are no measurements for a plot, don't try to plot measurements.

Also provides more informative messages if plotting fails.

Author: dweindl

petab/visualize/plotter.py

@@ -95,7 +95,8 @@ def generate_lineplot(
 
         label_base = dataplot.legendEntry
 
-        if measurements_to_plot is not None:
+        if measurements_to_plot is not None \
+                and not measurements_to_plot.data_to_plot.empty:
             # plotting all measurement data
 
             if plotTypeData == REPLICATE:
@@ -376,7 +377,11 @@ def generate_figure(
             else:
                 ax = axes[subplot.plotId]
 
-            self.generate_subplot(ax, subplot)
+            try:
+                self.generate_subplot(ax, subplot)
+            except Exception as e:
+                raise RuntimeError(
+                    f"Error plotting {getattr(subplot, PLOT_ID)}.") from e
 
             if subplot_dir is not None:
                 # TODO: why this doesn't work?