Do not crash when entering math in ct mode with merge dialog open.

Fixes: #7685.

src/BufferView.cpp

@@ -684,6 +684,10 @@ Change const BufferView::getCurrentChange() const
 		return Change(Change::UNCHANGED);
 
 	DocIterator dit = d->cursor_.selectionBegin();
+	// The selected content might have been changed (see #7685)
+	while (dit.inMathed())
+		// Find enclosing text cursor
+		dit.pop_back();
 	return dit.paragraph().lookupChange(dit.pos());
 }
 

status.21x

@@ -60,6 +60,9 @@ What's new
 
 * USER INTERFACE
 
+- Fix crash when entering math in change-tracking mode while merge changes
+  dialog is open (bug 7685).
+
 - Failed instant preview compilation now returns an error. And a red box is 
   drawn around very small preview imagines, so they can be seen (bug 7522).