Fix a memory leak; bug 17398.

changes/bug17398

@@ -0,0 +1,3 @@
+  o Minor bugfixes (memory leaks):
+    - Fix a memory leak in ed25519 batch signature checking.
+      Fixes bug 17398; bugfix on 0.2.6.1-alpha.

src/common/crypto_ed25519.c

@@ -260,6 +260,7 @@ ed25519_checksig_batch(int *okay_out,
     tor_free(ms);
     tor_free(lens);
     tor_free(pks);
+    tor_free(sigs);
     if (! okay_out)
       tor_free(oks);
   }