check non-null sensor in getCaptureOf(sensor)

src/frame/frame_base.cpp

@@ -274,9 +274,10 @@ CaptureBasePtr FrameBase::getCaptureOf(const SensorBasePtr _sensor_ptr, const st
 
 CaptureBasePtr FrameBase::getCaptureOf(const SensorBaseConstPtr _sensor_ptr) const
 {
-    for (CaptureBasePtr capture_ptr : getCaptureList())
-        if (capture_ptr->getSensor() == _sensor_ptr)
-            return capture_ptr;
+    if (_sensor_ptr)
+        for (CaptureBasePtr capture_ptr : getCaptureList())
+            if (capture_ptr->getSensor() == _sensor_ptr)
+                return capture_ptr;
     return nullptr;
 }