Issue #13545: Fix platform.libc_version() is the SO version is missing
diff --git a/Lib/platform.py b/Lib/platform.py
index 710f21e..20f8dc6 100755
--- a/Lib/platform.py
+++ b/Lib/platform.py
@@ -183,7 +183,7 @@
         elif so:
             if lib != 'glibc':
                 lib = 'libc'
-                if soversion > version:
+                if soversion and soversion > version:
                     version = soversion
                 if threads and version[-len(threads):] != threads:
                     version = version + threads