Returning a copy of installed libraries list, so clients can deal with it without incurring in concurrent list changes. See #3814

Author: Federico Fissore

arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java

@@ -216,7 +216,7 @@ public LibrariesIndex getIndex() {
   }
 
   public LibraryList getInstalledLibraries() {
-    return installedLibraries;
+    return new LibraryList(installedLibraries);
   }
 
   // Same as getInstalledLibraries(), but allow duplicates between
@@ -236,8 +236,6 @@ public File getStagingFolder() {
    * Set the sketchbook library folder. <br />
    * New libraries will be installed here. <br />
    * Libraries not found on this folder will be marked as read-only.
-   *
-   * @param folder
    */
   public void setSketchbookLibrariesFolder(File folder) {
     this.sketchbookLibrariesFolder = folder;