Fix typing

Signed-off-by: Arthur Chan <arthur.chan@adalogics.com>

src/fuzz_introspector/analyses/source_code_line_analyser.py

@@ -93,7 +93,7 @@ def standalone_analysis(self,
 
         if not self.source_file or self.source_line <= 0:
             logger.error('No valid source code or target line are provided')
-            return ''
+            return
 
         # Get all functions from the profiles
         all_functions = list(proj_profile.all_functions.values())
@@ -143,5 +143,3 @@ def standalone_analysis(self,
         else:
             logger.info('No functions found from line %d in %s',
                         self.source_line, self.source_file)
-
-        return ''