build: fix build on windows

isPasswordValid must return a boolean

Change-Id: I6465bfc73b08f203b2fa0b53deaf71b3406cabd6

src/jamidht/account_manager.h

@@ -121,7 +121,7 @@ public:
 
     virtual void syncDevices() = 0;
 
-    virtual bool isPasswordValid(const std::string& password) {};
+    virtual bool isPasswordValid(const std::string& password) { return false; };
 
     dht::crypto::Identity loadIdentity(const std::string& crt_path, const std::string& key_path, const std::string& key_pwd) const;