[LyX/master] Only write btUnits if we have a bibliography

[Juergen Spitzmueller]

commit b77094a497e64df0ef240ee3b6e04df1727a09f3
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Tue Apr 23 08:58:01 2019 +0200

    Only write btUnits if we have a bibliography
    
    Fixes: #11562
---
 src/output_latex.cpp |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/output_latex.cpp b/src/output_latex.cpp
index c231761..ab3760f 100644
--- a/src/output_latex.cpp
+++ b/src/output_latex.cpp
@@ -12,6 +12,7 @@
 
 #include "output_latex.h"
 
+#include "BiblioInfo.h"
 #include "Buffer.h"
 #include "BufferParams.h"
 #include "Encoding.h"
@@ -1436,7 +1437,8 @@ void latexParagraphs(Buffer const & buf,
 
        if (multibib_child && mparams.useBiblatex())
                os << "\\newrefsection";
-       else if (multibib_child && mparams.useBibtopic()) {
+       else if (multibib_child && mparams.useBibtopic()
+                && !buf.masterBibInfo().empty()) {
                os << "\\begin{btUnit}\n";
                runparams.openbtUnit = true;
        }
@@ -1546,7 +1548,8 @@ void latexParagraphs(Buffer const & buf,
                    && layout.latexname() == bparams.multibib) {
                        if (runparams.openbtUnit)
                                os << "\\end{btUnit}\n";
-                       if (!bparams.useBiblatex()) {
+                       if (!bparams.useBiblatex()
+                           && !buf.masterBibInfo().empty()) {
                                os << '\n' << "\\begin{btUnit}\n";
                                runparams.openbtUnit = true;
                        }