Merge: fix read from Zip file

Author: frodrigo

analysers/Analyser_Merge.py

@@ -352,6 +352,8 @@ def __init__(self, attribution = None, millesime = None, encoding = "utf-8", fil
             self.attribution_re = re.compile(self.attribution.replace("{0}", ".*"))
 
     def zipFile(self):
+        if not self.zip:
+            return None
         if self.file:
             f = open(self.file, 'rb')
         elif self.fileUrl: