FEM: Fix invalid check for empty resutls

Even when readResult was not producing any resuts the check was passing
fine as len({'Nodes': {}, 'Tet10Elem': {}, 'Results': []}) is 3

Signed-off-by: Przemo Firszt <przemo@firszt.eu>

src/Mod/Fem/ccxFrdReader.py

@@ -152,7 +152,7 @@ def importFrd(filename, Analysis=None):
     m = readResult(filename)
     result_set_number = len(m['Results'])
     MeshObject = None
-    if(len(m) > 0):
+    if(len(m['Nodes']) > 0):
         import Fem
         if Analysis is None:
             AnalysisName = os.path.splitext(os.path.basename(filename))[0]