fix memory leak in CKey::SetCompactSignature()

src/key.cpp

@@ -367,6 +367,7 @@ bool CKey::SetCompactSignature(uint256 hash, const std::vector<unsigned char>& v
         ECDSA_SIG_free(sig);
         return true;
     }
+    ECDSA_SIG_free(sig);
     return false;
 }