Fix crash when rendering ODS without depth export (fixes #418)

src/main/java/com/replaymod/render/capturer/ODSFrameCapturer.java

@@ -141,8 +141,10 @@ public class ODSFrameCapturer implements FrameCapturer<ODSOpenGlFrame> {
             for (Channel channel : Channel.values()) {
                 CubicOpenGlFrame leftFrame = leftChannels.get(channel);
                 CubicOpenGlFrame rightFrame = rightChannels.get(channel);
+                if (leftFrame != null && rightFrame != null) {
                     result.put(channel, new ODSOpenGlFrame(leftFrame, rightFrame));
                 }
+            }
             return result;
         }
         return null;