Fix #23 Revert a bug introduced with ab32fbbf98

Crash if checking for updates without an internet connection

CHANGELOG.md

@@ -4,7 +4,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 The first release is [3.0.0] because this is actually the third major version (completely rewritten) of the software.
 
 ## [Unreleased]
-...
+- Fixed crash on startup or if checking for updates without an internet connection ([#23](https://github.com/AresValley/Artemis/pull/23))
 
 ## [3.2.1] - 2020-04-25
 ### Added

src/versioncontroller.py

@@ -77,9 +77,14 @@ def _download_versions_file():
         }
     }
     """
-    return json.load(
+    try:
+        version_dict = json.load(
             BytesIO(download_file(Constants.VERSION_LINK))
-    ).get(get_os(), None)
+        )[get_os()]
+    except Exception:
+        return None
+    else:
+        return version_dict
 
 
 class VersionController: