Use emptry string if there is no name or email for the commit author

Issue #6

src/entity/commit.py

@@ -94,12 +94,14 @@ def set_commit_stats(self, stats):
 
     def obfuscate(self):
         if not self.skip_obfuscation:
-            md5_hash = md5.md5()
-            md5_hash.update(self.author_name.encode('utf-8'))
-            self.author_name = md5_hash.hexdigest()
-            md5_hash = md5.md5()
-            md5_hash.update(self.author_email.encode('utf-8'))
-            self.author_email = md5_hash.hexdigest()
+            if self.author_name is not None:
+                md5_hash = md5.md5()
+                md5_hash.update(self.author_name.encode('utf-8'))
+                self.author_name = md5_hash.hexdigest()
+            if self.author_email is not None:
+                md5_hash = md5.md5()
+                md5_hash.update(self.author_email.encode('utf-8'))
+                self.author_email = md5_hash.hexdigest()
 
     def json_ready(self):
         changed_files = []

src/entity/repository.py

@@ -34,9 +34,15 @@ def __init__(self, repo_name, repo, commits):
         self.number_of_tags = len(repo.tags)
         self.commits = []
         for hash in commits:
-            self.contributors[commits[hash].original_author_name + commits[hash].original_author_email] = {
-                'name': commits[hash].original_author_name,
-                'email': commits[hash].original_author_email
+            name = ""
+            email = ""
+            if commits[hash].original_author_name is not None:
+                name = commits[hash].original_author_name 
+            if commits[hash].original_author_email is not None:
+                email = commits[hash].original_author_email
+            self.contributors[name + email] = {
+                'name': name,
+                'email': email
             }
             self.commits.append(commits[hash])