[LyX/2.3.x] Fix Null-checking issue detected by Coverity.

[Juergen Spitzmueller]

commit 9e8d702d634fc046bda0b480ee652e97094fa831
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Thu Jan 11 13:43:35 2018 +0100

    Fix Null-checking issue detected by Coverity.
    
    (cherry picked from commit 974553d8583954aa7741c4dc0ce83f9ca812b03b)
---
 src/Paragraph.cpp |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/Paragraph.cpp b/src/Paragraph.cpp
index fcf4a73..5c5a728 100644
--- a/src/Paragraph.cpp
+++ b/src/Paragraph.cpp
@@ -1436,9 +1436,6 @@ bool Paragraph::Private::latexSpecialT3(char_type const 
c, otexstream & os,
 
 void Paragraph::Private::validate(LaTeXFeatures & features) const
 {
-       Buffer const & buf = inset_owner_->buffer();
-       BufferParams const & bp = features.runparams().is_child
-               ? buf.masterParams() : buf.params();
        if (layout_->inpreamble && inset_owner_) {
                bool const is_command = layout_->latextype == LATEX_COMMAND;
                Font f;
@@ -1446,6 +1443,9 @@ void Paragraph::Private::validate(LaTeXFeatures & 
features) const
                // switching machinery of odocstream. Therefore the
                // output is wrong if this paragraph contains content
                // that needs to switch encoding.
+               Buffer const & buf = inset_owner_->buffer();
+               BufferParams const & bp = features.runparams().is_child
+                       ? buf.masterParams() : buf.params();
                otexstringstream os;
                os << layout_->preamble();
                if (is_command) {
@@ -1520,6 +1520,8 @@ void Paragraph::Private::validate(LaTeXFeatures & 
features) const
        }
 
        // then the contents
+       BufferParams const bp = features.runparams().is_child
+               ? features.buffer().masterParams() : features.buffer().params();
        for (pos_type i = 0; i < int(text_.size()) ; ++i) {
                char_type c = text_[i];
                if (c == 0x0022) {