Don't add bad corners to multi-tag solution (#817)

Closes #837


---------

Co-authored-by: Chris Gerth <gerth2@users.noreply.github.com>

photon-lib/src/main/native/cpp/photonlib/PhotonPoseEstimator.cpp

@@ -391,8 +391,9 @@ std::optional<EstimatedRobotPose> PhotonPoseEstimator::MultiTagPnpStrategy(
     }
   }
 
-  if (imagePoints.empty()) {
-    return std::nullopt;
+  // We should only do multi-tag if at least 2 tags (* 4 corners/tag)
+  if (imagePoints.size() < 8) {
+    return Update(result, camMat, distCoeffs, this->multiTagFallbackStrategy);
   }
 
   // Use OpenCV ITERATIVE solver