General warning cleanup

src/main/java/eu/crushedpixel/replaymod/assets/AssetFileUtils.java

@@ -14,7 +14,7 @@ public class AssetFileUtils {
             return ImageIO.getReaderFileSuffixes();
         }
 
-        return null;
+        throw new UnsupportedOperationException("Unknown replay asset type: " + clazz);
     }
 
     public static String[] getAllAvailableExtensions() {

src/main/java/eu/crushedpixel/replaymod/assets/CustomImageObject.java

@@ -91,7 +91,7 @@ public class CustomImageObject implements GuiEntryListEntry {
             return null;
         }
 
-        if(resourceLocation != null && !ResourceHelper.isRegistered(resourceLocation)) {
+        if(!ResourceHelper.isRegistered(resourceLocation)) {
             ResourceHelper.registerResource(resourceLocation);
             Minecraft.getMinecraft().getTextureManager().loadTexture(resourceLocation, dynamicTexture);
             dynamicTexture.updateDynamicTexture();