Make sure DiscoveryManager is not null when calling it

Solves #5413

Author: facchinm

arduino-core/src/processing/app/BaseNoGui.java

@@ -210,6 +210,9 @@ static public  File getDefaultSketchbookFolder() {
   }
 
   public static DiscoveryManager getDiscoveryManager() {
+    if (discoveryManager == null) {
+      discoveryManager = new DiscoveryManager();
+    }
     return discoveryManager;
   }
 
@@ -633,7 +636,9 @@ static public void initPackages() throws Exception {
       FileUtils.deleteIfExists(librariesIndexFile);
     }
 
-    discoveryManager = new DiscoveryManager();
+    if (discoveryManager == null) {
+      discoveryManager = new DiscoveryManager();
+    }
   }
 
   static protected void initPlatform() {