Fix typo in engine.py

- Add protection for empty hash digests in comparison of non-zero size
  files
- Bump version to 4.3.1-dev for identification

core/__init__.py

@@ -1,2 +1,2 @@
-__version__ = "4.3.0"
+__version__ = "4.3.1-dev"
 __appname__ = "dupeGuru"

core/engine.py

@@ -303,12 +303,13 @@ def getmatches_by_contents(files, bigsize=0, j=job.nulljob):
                 # skip hashing for zero length files
                 result.append(Match(first, second, 100))
                 continue
-            if first.digest_partial == second.digest_partial:
+            # if digests are the same (and not None) then files match
+            if first.digest_partial == second.digest_partial and first.digest_partial is not None:
                 if bigsize > 0 and first.size > bigsize:
-                    if first.digest_samples == second.digest_samples:
+                    if first.digest_samples == second.digest_samples and first.digest_samples is not None:
                         result.append(Match(first, second, 100))
                 else:
-                    if first.digest == second.digest:
+                    if first.digest == second.digest and first.digest is not None:
                         result.append(Match(first, second, 100))
         group_count += 1
         j.add_progress(desc=PROGRESS_MESSAGE % (len(result), group_count))