[LyX/master] Make sure we have a buffer in VC_COMPARE.

[Richard Heck]

commit 2cb6ed93768faa2f8ae5f5bb27b5b8b50cf036d2
Author: Richard Heck <rgh...@lyx.org>
Date:   Sat Jun 11 22:41:57 2016 -0400

    Make sure we have a buffer in VC_COMPARE.
    
    Fixes coverity #23304.

diff --git a/src/frontends/qt4/GuiView.cpp b/src/frontends/qt4/GuiView.cpp
index af7419d..fc2170d 100644
--- a/src/frontends/qt4/GuiView.cpp
+++ b/src/frontends/qt4/GuiView.cpp
@@ -3241,7 +3241,6 @@ void GuiView::dispatchVC(FuncRequest const & cmd, 
DispatchResult & dr)
                }
 
        case LFUN_VC_COMPARE: {
-
                if (cmd.argument().empty()) {
                        lyx::dispatch(FuncRequest(LFUN_DIALOG_SHOW, 
"comparehistory"));
                        break;
@@ -3251,6 +3250,8 @@ void GuiView::dispatchVC(FuncRequest const & cmd, 
DispatchResult & dr)
                string f1, f2;
 
                // f1
+               // it seems safe to assume we have a buffer
+               // coverity[FORWARD_NULL]
                if (!buffer->lyxvc().prepareFileRevision(rev1, f1))
                        break;