Fixed application hanging for iris depth example when no face is in the input image

mediapipe/calculators/util/non_max_suppression_calculator.cc

@@ -199,6 +199,9 @@ class NonMaxSuppressionCalculator : public CalculatorBase {
       if (options_.return_empty_detections()) {
         cc->Outputs().Index(0).Add(new Detections(), cc->InputTimestamp());
       }
+      if (options_.error_on_empty_detections()) {
+        return ::mediapipe::InternalError("NonMaxSuppression received empty detections, but detections are required for this pipeline.");
+       }
       return ::mediapipe::OkStatus();
     }
 

mediapipe/calculators/util/non_max_suppression_calculator.proto

@@ -58,6 +58,9 @@ message NonMaxSuppressionCalculatorOptions {
   // Whether to put empty detection vector in output stream.
   optional bool return_empty_detections = 5;
 
+  // Whether to throw an error on an empty input detection vector
+  optional bool error_on_empty_detections = 8;
+
   // Algorithms that can be used to apply non-maximum suppression.
   enum NmsAlgorithm {
     DEFAULT = 0;

mediapipe/modules/face_detection/face_detection_front_cpu.pbtxt

@@ -128,6 +128,7 @@ node {
       min_suppression_threshold: 0.3
       overlap_type: INTERSECTION_OVER_UNION
       algorithm: WEIGHTED
+      error_on_empty_detections: true
     }
   }
 }