[LyX/master] Fix another crash similar to #9030

[Georg Baum]

commit 85db1005b621aa7895c230e07bcf92e8ca041e7b
Author: Georg Baum <b...@lyx.org>
Date:   Thu May 22 22:00:58 2014 +0200

    Fix another crash similar to #9030
    
    This one occured after the fix for bug #9030 if the cursor is in a math 
inset
    and the edit menu is opened.

diff --git a/src/frontends/qt4/Menus.cpp b/src/frontends/qt4/Menus.cpp
index 7911c16..110121c 100644
--- a/src/frontends/qt4/Menus.cpp
+++ b/src/frontends/qt4/Menus.cpp
@@ -1665,9 +1665,13 @@ void 
MenuDefinition::expandEnvironmentSeparators(BufferView const * bv)
 {
        if (!bv)
                return;
+       Text const * text = bv->cursor().text();
+       // no paragraphs and no separators exist in math
+       if (!text)
+               return;
 
        pit_type pit = bv->cursor().selBegin().pit();
-       Paragraph const & par = bv->cursor().text()->getPar(pit);
+       Paragraph const & par = text->getPar(pit);
        docstring const curlayout = par.layout().name();
        docstring outerlayout;
        depth_type current_depth = par.params().depth();
@@ -1677,7 +1681,7 @@ void 
MenuDefinition::expandEnvironmentSeparators(BufferView const * bv)
                if (pit == 0 || cpar.params().depth() == 0)
                        break;
                --pit;
-               cpar = bv->cursor().text()->getPar(pit);
+               cpar = text->getPar(pit);
                if (cpar.params().depth() < current_depth
                    && cpar.layout().isEnvironment()) {
                                outerlayout = cpar.layout().name();