[FREELDR] Reset BootType before reading its value in the freeldr.ini OS section, if it exists

Because if the value doesn't exist in the OS section, the value isn't
reset and the code would reuse a stray one that was for the previous entry.

boot/freeldr/freeldr/oslist.c

@@ -161,6 +161,7 @@ InitOperatingSystemList(
         if (HadSection)
         {
             /* This is a new OS entry: try to read the boot type */
+            *BootType = ANSI_NULL;
             IniReadSettingByName(SectionId, "BootType", BootType, sizeof(BootType));
         }
         else