Analytics works with one labeled segment#191/212 (#217)

* Analytics works with one labeled segment

if/else instead of exception

analytics/utils/__init__.py

@@ -212,7 +212,7 @@ def ar_mean(numbers):
 
 def get_av_model(patterns_list):
     x = len(patterns_list[0])
-    if len(patterns_list[1]) != x:
+    if len(pattern_list) > 1 and len(patterns_list[1]) != x:
         raise NameError('All elements of patterns_list should have same length')
     model_pat = []
     for i in range(x):