A few more constants to avoid copies

diff --git a/src/insets/InsetBibtex.cpp b/src/insets/InsetBibtex.cpp
index 876adea54b1770ad15a140a3a8d50eb2890edff5..34b22c1583f8a24788768987878a3b00b7894782 100644 (file)
--- a/src/insets/InsetBibtex.cpp
+++ b/src/insets/InsetBibtex.cpp
@@ -1216,9 +1216,9 @@ void InsetBibtex::docbook(XMLStream & xs, OutputParams const &) const
                if (! delayedTags.empty()) {
                        unsigned long remainingTags = delayedTags.size(); // Used as a workaround. With GCC 7, when erasing all
                        // elements one by one, some elements may still pop in later on (even though they were deleted previously).
-                       auto hasTag = [&delayedTags](string key) { return delayedTags.find(key) != delayedTags.end(); };
-                       auto getTag = [&delayedTags](string key) { return from_utf8(delayedTags[key]); };
-                       auto eraseTag = [&delayedTags, &remainingTags](string key) {
+                       auto hasTag = [&delayedTags](const string & key) { return delayedTags.find(key) != delayedTags.end(); };
+                       auto getTag = [&delayedTags](const string & key) { return from_utf8(delayedTags[key]); };
+                       auto eraseTag = [&delayedTags, &remainingTags](const string & key) {
                                remainingTags -= 1;
                                delayedTags.erase(key);
                        };