check for keylength and not presence of one specific key in the qdp plotter for determining whether to merge times for scan b and scan a

qdp_project/plotter.py

@@ -31,7 +31,7 @@ def read_timings_from_csv(fname, fn_nice) -> tuple[list[float], list[str]]:
 
     t = {key: value / (1000 * 1000 * row_count) for key, value in t.items() if value != 0}
 
-    if fn_nice[2] in t.keys():
+    if len(t.keys()) == 3:
         t[fn_nice[1]] = t[fn_nice[1]] - t[fn_nice[2]]
 
     return list(t.values()), list(t.keys())