Fix build error in shop name generator

crawl-ref/source/shopping.cc

@@ -1569,8 +1569,8 @@ pair<string, string> generate_shop_name(shop_type type, int shop_level, bool goz
     // depending on how it was generated, so it can get up to 54 with Gozag.
     // We can generate some pretty succinct names so let's start at 16 and go up to 70
     // at max (any more than this would cause display issues anyway).
-    const uint target_max = 20 + shop_level;
-    const uint target_min = 20 - shop_level / 3;
+    const int target_max = 20 + shop_level;
+    const int target_min = 20 - shop_level / 3;
     const size_t target_length = random_range(target_min, target_max);
     const bool fancy = shop_level >= 20; // Orc shops will qualify as "fancy"
     string key = shop_type_name(type) + " shop name";