systemsp: initialize media name and default eeprom

Fix failure to load a systemsp rom game after running a compactflash
game.
Fix error 05 if selecting the wrong region then switching to Japan.

core/hw/naomi/naomi_cart.cpp

@@ -757,6 +757,7 @@ void naomi_cart_Close()
 	CurrentCartridge = nullptr;
 	NaomiGameInputs = nullptr;
 	bios_loaded = false;
+	naomi_default_eeprom = nullptr;
 }
 
 void naomi_cart_serialize(Serializer& ser)

core/hw/naomi/systemsp.h

@@ -182,8 +182,8 @@ private:
 	}
 
 	int schedId;
-	const char *mediaName;
-	const char *parentName;
+	const char *mediaName = nullptr;
+	const char *parentName = nullptr;
 	FILE *chdFile = nullptr;
 	chd_file *chd = nullptr;
 	u32 hunkbytes = 0;