Treat generation 0 a bit specially.

I guess we could always check gen 0 first, that'd be readahead/backfill.

Core/Loaders.cpp

@@ -538,11 +538,12 @@ bool CachingFileLoader::MakeCacheSpaceFor(size_t blocks, bool readingAhead) {
 		for (auto it = blocks_.begin(); it != blocks_.end(); ) {
 			// Check for the minimum seen generation.
 			// TODO: Do this smarter?
-			if (it->second.generation < minGeneration) {
+			if (it->second.generation != 0 && it->second.generation < minGeneration) {
 				minGeneration = it->second.generation;
 			}
 
-			if (it->second.generation == oldestGeneration_) {
+			// 0 means it was never used yet or was the first read (e.g. block descriptor.)
+			if (it->second.generation == oldestGeneration_ || it->second.generation == 0) {
 				s64 pos = it->first;
 				delete it->second.ptr;
 				blocks_.erase(it);