Fixed incorrect priority modulo results.

The modulo operation a % b isn't implemented as expected when
a is an int and b is an unsigned int, so make sure they're the
same type.

src/backend/metadata/plugin_metadata.h

@@ -43,7 +43,7 @@
 #include <yaml-cpp/yaml.h>
 
 namespace loot {
-    const unsigned int max_priority = 1000000;
+    const int max_priority = 1000000;
 
     class Game;