zdc_lambda: run even more code conditionally (#142)

benchmarks/zdc_lambda/analysis/lambda_plots.py

@@ -60,7 +60,9 @@ for p in momenta:
 
 if "ReconstructedFarForwardZDCLambdas.momentum.x" not in arrays_sim[momenta[0]].fields:
     print("ReconstructedFarForwardZDCLambdas collection is not available (needs EICrecon 1.23)")
-else:
+    import sys
+    sys.exit(0)
+
 theta_recon={}
 E_recon={}
 zvtx_recon={}