fix(plugins): Don't crash when result is None

The idea here as to have the symmetry that when result is None
the tags would also be None.
While I like this in general this was not thought out.
The get_tags signature did not allow this and the rest of the codebase
was not build with this in mind.

src/analysis/plugin/plugin.py

@@ -125,7 +125,7 @@ def get_analysis(self, file_handle: io.FileIO, virtual_file_path: dict, analyses
         result = self.analyze(file_handle, virtual_file_path, analyses)
 
         summary = None
-        tags = None
+        tags = []
         if result is not None:
             summary = self.summarize(result)
             tags = self.get_tags(result, summary)