title: Eclipse: in the Libraries tab all buttons are disabled
body: <p>I am using Eclipse Oxygen.2 (4.7.2) and Java 9.0.4. I created a project via right-click <em>> Build Path > Configure Build Path... > Libraries</em>. All buttons are disabled like <em>Add JARs</em>, *Add External JARs..., etc.:</p>
  
  <p><a href="https://i.stack.imgur.com/ZE6Vi.png" rel="noreferrer"><img src="https://i.stack.imgur.com/ZE6Vi.png" alt="screen shot of error page "></a></p>
  
  <p>Please help me to solve this issue. </p>