### Describe the issue
In Bitcoin QT, under the Transactions tab when right clicking on the transaction the context menu shows more option then it can always handle.

### Can you reliably reproduce the issue?
Yes.

#### If so, please list the steps to reproduce below:  
0. Open QT.  
1. Make an incoming transaction without label.  
2. Go to the Transactions tab.  
3. Rigth click on a transaction and select "Copy label".  

### Actual behaviour
The clipboard will be empty.  

### Expected behaviour
Copies the label. (What does not exist, of course.)

### What version of bitcoin-core are you using?
v0.13.1, Ubuntu PPA.  

### Any extra information that might be useful in the debugging process.
This behaviour is more problematic in edge cases.  
Like when you send funds with JoinMarket. In this case for example the "Copy address" option does not work.  

### Suggestion
I think when something cannot be copied that should not be present in the context menu in the first place.  
  
![](http://i.imgur.com/hLfAgeF.png)
void dateRangeChanged();
    void showDetails();
    void copyAddress();
    void editLabel();
    void copyLabel();
    void copyAmount();
    void copyTxID();
    void copyTxHex();
    void copyTxPlainText();
    void openThirdPartyTxUrl(QString url);
    void updateWatchOnlyColumn(bool fHaveWatchOnly);
    void abandonTx();
    void bumpFee();
Q_SIGNALS:
    void doubleClicked(const QModelIndex&);
    
    void message(const QString &title, const QString &message, unsigned int style);
    void bumpedFee(const uint256& txid);
public Q_SLOTS:
    void chooseDate(int idx);
    void chooseType(int idx);
    void chooseWatchonly(int idx);
    void changedAmount();
    void changedSearch();
    void exportClicked();
    void focusTransaction(const QModelIndex&);
    void focusTransaction(const uint256& txid);
};
#endif