Fixed NPE when trying to open a downloaded file with an empty replay_recordings folder

src/main/java/eu/crushedpixel/replaymod/gui/online/GuiReplayInstanceChooser.java

@@ -50,7 +50,9 @@ public class GuiReplayInstanceChooser extends GuiScreen {
 
             List<File> chooseableFiles = new ArrayList<File>();
 
-            for(File file : replayFolder.listFiles()) {
+            File[] files = replayFolder.listFiles();
+            if(files != null) {
+                for(File file : files) {
                     try {
                         String extension = FilenameUtils.getExtension(file.getAbsolutePath());
                         if(!("." + extension).equals(ReplayFile.ZIP_FILE_EXTENSION)) continue;
@@ -66,6 +68,7 @@ public class GuiReplayInstanceChooser extends GuiScreen {
                         e.printStackTrace();
                     }
                 }
+            }
 
             //if no modified versions of the replay were found, start the downloaded one
             if(chooseableFiles.isEmpty()) {