eval-cache: fix parsing of contexts

The members of the context were serialized with a space as the delimiter, not a semicolon.

Signed-off-by: Connor Baker <ConnorBaker01@gmail.com>

src/libexpr/eval-cache.cc

@@ -265,7 +265,7 @@ struct AttrDb
         case AttrType::String: {
             NixStringContext context;
             if (!queryAttribute.isNull(3))
-                for (auto & s : tokenizeString<std::vector<std::string>>(queryAttribute.getStr(3), ";"))
+                for (auto & s : tokenizeString<std::vector<std::string>>(queryAttribute.getStr(3), " "))
                     context.insert(NixStringContextElem::parse(s));
             return {{rowId, string_t{queryAttribute.getStr(2), context}}};
         }