fix: [LaughFE] restore check for input files

pipeline/feature_extractors.py

@@ -107,6 +107,8 @@ class LaughterFeatureExtractor(FeatureExtractor):
 
         jrgillick's laughter-detection library can work with AV files directly!
         """
+        if not self.input_files or len(self.input_files) == 0:
+            raise ValueError("No input files provided!")
 
 
     def run(self):