Fix the real root cause, files not containing a banner.

volatility/framework/automagic/linux.py

@@ -41,7 +41,7 @@ class LinuxSymbolFinder(interfaces.automagic.AutomagicInterface):
         if not self._linux_banners:
             return
 
-        mss = scanners.MultiStringScanner(list(self._linux_banners))
+        mss = scanners.MultiStringScanner([x for x in self._linux_banners if x is not None])
 
         layer = context.memory[layer_name]
 

volatility/framework/automagic/linux_symbol_cache.py

@@ -29,8 +29,6 @@ class LinuxSymbolCache(interfaces.automagic.AutomagicInterface):
                     vollog.log(constants.LOGLEVEL_V,
                                "Removing cached path {} for banner {}: files does not exist".format(path, banner))
                     linuxbanners[banner].remove(path)
-        # Rewrite it in case we found any files that were no logner present
-        cls.save_linux_banners(linuxbanners)
         return linuxbanners
 
     @classmethod