Avoid to delete unexistent paths [JENKINS-37500]

Signed-off-by: Marco Nenciarini <marco.nenciarini@2ndquadrant.it>
Signed-off-by: Giulio Calacoci <giulio.calacoci@2ndquadrant.it>

Author: mnencia

src/main/java/hudson/plugins/scm_sync_configuration/model/ChangeSet.java

@@ -58,8 +58,10 @@ public void registerPath(String path) {
     public void registerPathForDeletion(String path){
         // We should determine if path is a directory by watching scm path (and not hudson path) because in most of time,
         // when we are here, directory is already deleted in hudson hierarchy...
-        boolean isDirectory = new Path(path).getScmFile().isDirectory();
-        pathsToDelete.add(new Path(path, isDirectory));
+        if(new Path(path).getScmFile().exists()) {
+            boolean isDirectory = new Path(path).getScmFile().isDirectory();
+            pathsToDelete.add(new Path(path, isDirectory));
+        }
     }
 
     public boolean isEmpty(){