Ignores 0 in custom atlas - fixes an issue with QuPath (and that can make sense)

Author: NicoKiaru

src/main/java/ch/epfl/biop/atlas/custom/AtlasFromSourcesHelper.java

@@ -189,6 +189,7 @@ public String getName() {
             @Override
             public void initialize() throws Exception {
                 HashSet<Integer> values = getUniquePixelValues(labelImage);
+                values.remove(0); // Causes issues otherwise
                 int rootIdTest = 1024;
                 while (values.contains(rootIdTest)) {
                     rootIdTest*=2;