[LyX/2.3.2-2] Fix problem reported on the mailing list.

[Richard Kimberly Heck]

commit 4404f0bab2b7faf1a9d69e70e57e2e41c4def4d7
Author: Richard Kimberly Heck <rikih...@lyx.org>
Date:   Sun Dec 30 14:02:34 2018 -0500

    Fix problem reported on the mailing list.
    
    Somehow this got lost. Fix found by Jürgen.
---
 src/Buffer.cpp |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 6343405..e248348 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -2457,6 +2457,11 @@ void Buffer::checkIfBibInfoCacheIsValid() const
                return;
        }
 
+       // if we already know the cache is invalid, no need to check
+       // the timestamps
+       if (!d->bibinfo_cache_valid_)
+               return;
+
        // we'll assume it's ok and change this if it's not
        d->bibinfo_cache_valid_ = true;
        d->cite_labels_valid_ = true;