basic/ex05: skip if total_energy not found

We do this in test/workflow_test.py, so seems sensible to do it here as well.

Author: elcorto

examples/basic/ex05_run_predictions.py

@@ -1,4 +1,5 @@
 import os
+from importlib.util import find_spec
 
 from ase.io import read
 import mala
@@ -39,7 +40,11 @@
 ldos_calculator: mala.LDOS = predictor.target_calculator
 ldos_calculator.read_from_array(ldos)
 printout("Predicted band energy: ", ldos_calculator.band_energy)
+
 # If the total energy module is installed, the total energy can also be
 # calculated.
-# parameters.targets.pseudopotential_path = data_path
-# printout("Predicted total energy", ldos_calculator.total_energy)
+if find_spec("total_energy"):
+    parameters.targets.pseudopotential_path = data_path
+    printout("Predicted total energy", ldos_calculator.total_energy)
+else:
+    print("total_energy module not found, skipping total energy calculation")