Update src/aliceVision/sfmDataIO/UsdExporter.cpp

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: servantftransperfect

src/aliceVision/sfmDataIO/UsdExporter.cpp

@@ -38,8 +38,18 @@ UsdExporter::UsdExporter(const std::string & filename, double frameRate)
 
 void UsdExporter::terminate()
 {
-    _stage->SetStartTimeCode(_startTimeCode);
-    _stage->SetEndTimeCode(_endTimeCode);       
+    // If no frames have been exported, _startTimeCode will still be at its sentinel value.
+    // In that case, avoid writing invalid start/end time codes to the USD stage.
+    if (_startTimeCode == std::numeric_limits<IndexT>::max())
+    {
+        ALICEVISION_LOG_WARNING("UsdExporter::terminate called but no frames have been exported; "
+                                "skipping start/end time code settings.");
+    }
+    else
+    {
+        _stage->SetStartTimeCode(_startTimeCode);
+        _stage->SetEndTimeCode(_endTimeCode);
+    }
 
     _stage->Save();
 }