Fixed: Artist Type can be null/blank

frontend/src/Artist/Details/ArtistDetails.js

@@ -680,7 +680,7 @@ ArtistDetails.propTypes = {
   statistics: PropTypes.object.isRequired,
   qualityProfileId: PropTypes.number.isRequired,
   monitored: PropTypes.bool.isRequired,
-  artistType: PropTypes.string.isRequired,
+  artistType: PropTypes.string,
   albumTypes: PropTypes.arrayOf(PropTypes.string),
   status: PropTypes.string.isRequired,
   overview: PropTypes.string.isRequired,

frontend/src/Artist/Editor/ArtistEditorRow.js

@@ -101,7 +101,7 @@ ArtistEditorRow.propTypes = {
   status: PropTypes.string.isRequired,
   foreignArtistId: PropTypes.string.isRequired,
   artistName: PropTypes.string.isRequired,
-  artistType: PropTypes.string.isRequired,
+  artistType: PropTypes.string,
   monitored: PropTypes.bool.isRequired,
   metadataProfile: PropTypes.object.isRequired,
   qualityProfile: PropTypes.object.isRequired,

frontend/src/Artist/Index/Table/ArtistStatusCell.js

@@ -39,7 +39,7 @@ function ArtistStatusCell(props) {
 
 ArtistStatusCell.propTypes = {
   className: PropTypes.string.isRequired,
-  artistType: PropTypes.string.isRequired,
+  artistType: PropTypes.string,
   monitored: PropTypes.bool.isRequired,
   status: PropTypes.string.isRequired,
   component: PropTypes.elementType