sqlite: add a Use::fromStrNullable

There were several usages of the raw sqlite primitives along with C
style casts, seemingly because nobody thought to use an optional for
getting a string or NULL.

Let's fix this API given we already *have* a wrapper.

Change-Id: I526cceedc2e356209d8fb62e11b3572282c314e8

1 files changed, 1 insertions, 0 deletions

diff --git a/src/libstore/sqlite.hh b/src/libstore/sqlite.hh
index 003e4d101..ca021087f 100644
--- a/src/libstore/sqlite.hh
+++ b/src/libstore/sqlite.hh
@@ -107,6 +107,7 @@ struct SQLiteStmt
         bool next();
 
         std::string getStr(int col);
+        std::optional<std::string> getStrNullable(int col);
         int64_t getInt(int col);
         bool isNull(int col);
     };