Coverity issues:

129202: replace dynamic_cast with static_cast
129421, 129422: fix Py_Return macro
128928: Unchecked return value
129488, 129490: uninitialized scalar variable
129567, 129661: uninitialized scalar field
129665: uninitialized pointer field

src/App/MergeDocuments.cpp

@@ -97,7 +97,7 @@ private:
 };
 }
 
-MergeDocuments::MergeDocuments(App::Document* doc) : guiup(false), appdoc(doc)
+MergeDocuments::MergeDocuments(App::Document* doc) : guiup(false), verbose(true), stream(0), appdoc(doc)
 {
     connectExport = doc->signalExportObjects.connect
         (boost::bind(&MergeDocuments::exportObject, this, _1, _2));