More SonarQube detected bugs fixed:

- Use try-with-resources in AutoCloseable objects.
- End this switch case with an unconditional break, return or throw statement.
- A "NullPointerException" could be thrown.
- Use the "equals" method if value comparison was intended.
- Correct this "&" to "&&".

forge-gui-desktop/src/main/java/forge/toolbox/SaveOpenDialog.java

@@ -111,7 +111,7 @@ public class SaveOpenDialog extends JPanel {
             RetFile = fc.getSelectedFile();
 
             /* Adds extension if it is known and not given */
-            if (type != null & !(RetFile.getAbsolutePath().endsWith(type.TypeExtension))) {
+            if (type != null && !(RetFile.getAbsolutePath().endsWith(type.TypeExtension))) {
                 RetFile = new File(RetFile.getAbsolutePath() + "." + type.TypeExtension);
             }