[LyX/master] Fixup 522516d9 : editable() is unusable in mathed

[Jean-Marc Lasgouttes]

commit d0acc3e570447b293169b8bdd5ac67aaade189e0
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Tue Jun 20 09:41:48 2017 +0200

    Fixup 522516d9 : editable() is unusable in mathed
    
    This is a relic from IU (Inset Unification): editable() is for text
    insets and isActive() for mathed. This needs to be cleaned up.
    
    Part of bug #10667.
---
 src/DocIterator.cpp |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/DocIterator.cpp b/src/DocIterator.cpp
index 3d9bd68..fe1250f 100644
--- a/src/DocIterator.cpp
+++ b/src/DocIterator.cpp
@@ -562,7 +562,7 @@ bool DocIterator::fixIfBroken()
        size_t n = slices_.size();
        for (; i != n; ++i) {
                CursorSlice & cs = slices_[i];
-               if (&cs.inset() != inset || !cs.inset().editable()) {
+               if (&cs.inset() != inset || cs.nargs() == 0) {
                        // the whole slice is wrong, chop off this as well
                        --i;
                        LYXERR(Debug::DEBUG, "fixIfBroken(): inset changed");