StreamMergeApp: fix VPS allocation issue

A pointer to a local VPS is passed as reference into the parameter set manager, which takes ownership of the object.
When the local scope is left, the memory will be freed, which can lead to use after free (and double free).

source/App/StreamMergeApp/StreamMergeApp.cpp

@@ -544,12 +544,12 @@ uint32_t StreamMergeApp::mergeStreams()
     // Prep other values.
     layer.bs = new InputByteStream(*(layer.fp));
 
-    VPS vps;
-    vps.setMaxLayers((uint32_t) layers->size());
-    vps.setLayerId(layer.id, layer.id);   // Layer ID is rewritten here.
-    layer.vpsIdMapping.insert({ vps.getVPSId(), 0 });
-    vps.setVPSId(0);
-    layer.psManager.storeVPS(&vps, std::vector<uint8_t>()); // Create VPS with default values (VTM slice header parser needs this)
+    VPS* vps = new VPS;
+    vps->setMaxLayers((uint32_t) layers->size());
+    vps->setLayerId(layer.id, layer.id);   // Layer ID is rewritten here.
+    layer.vpsIdMapping.insert({ vps->getVPSId(), 0 });
+    vps->setVPSId(0);
+    layer.psManager.storeVPS(vps, std::vector<uint8_t>()); // Create VPS with default values (VTM slice header parser needs this)
   }
 
   // Loop over layers until every one is entirely read.