MM: some assertion on MM input

Change-Id: Id29ede49acf86ad6109eab88fbae5d9bbb2d8720

sw/inc/dbmgr.hxx

@@ -182,8 +182,10 @@ struct SwMergeDescriptor
         bPrintAsync( false ),
         bCreateSingleFile( false ),
         pMailMergeConfigItem(nullptr)
-        {}
-
+    {
+        if( nType == DBMGR_MERGE_SHELL )
+            bCreateSingleFile = true;
+    }
 };
 
 struct SwDBManager_Impl;

sw/source/uibase/dbui/dbmgr.cxx

@@ -950,7 +950,19 @@ bool SwDBManager::MergeMailFiles(SwWrtShell* pSourceShell,
     //check if the doc is synchronized and contains at least one linked section
     const bool bSynchronizedDoc = pSourceShell->IsLabelDoc() && pSourceShell->GetSectionFormatCount() > 1;
     const bool bNeedsTempFiles = ( bMT_EMAIL || bMT_FILE );
-    const bool bCreateSingleFile = rMergeDescriptor.bCreateSingleFile;
+
+    bool bCheckSingleFile_ = rMergeDescriptor.bCreateSingleFile;
+    if( bMT_EMAIL )
+    {
+        assert( bMT_EMAIL && !bCheckSingleFile_ );
+        bCheckSingleFile_ = false;
+    }
+    else if( bMT_SHELL )
+    {
+        assert( bMT_SHELL && bCheckSingleFile_ );
+        bCheckSingleFile_ = true;
+    }
+    const bool bCreateSingleFile = bCheckSingleFile_;
 
     // Setup for dumping debugging documents
     static const char *sMaxDumpDocs = nullptr;