Ensure drive is not null for volume labels (fixes #356)

CHANGELIST.md

@@ -77,6 +77,7 @@
 - Ensure Games pseudo-tag is multi-line
 - Add alternate pseudo-tag for Playable Demos
 - Make error clearer if something is unsupported in Check
+- Ensure drive is not null for volume labels
 
 ### 2.2 (2021-12-30)
 - Fix Saturn header finding

MPF.Library/InfoTool.cs

@@ -104,7 +104,8 @@ namespace MPF.Library
                 info.TracksAndWriteOffsets.ClrMameProData = null;
 
             // Add the volume label to comments, if possible or necessary
-            if (drive.GetRedumpSystemFromVolumeLabel() == null
+            if (drive != null
+                && drive.GetRedumpSystemFromVolumeLabel() == null
                 && !info.CommonDiscInfo.CommentsSpecialFields.ContainsKey(SiteCode.VolumeLabel))
             {
                 info.CommonDiscInfo.CommentsSpecialFields[SiteCode.VolumeLabel] = drive.VolumeLabel;