Show warning when using the docker update mechanism

(cherry picked from commit cc538c4b2d33a1734c45c0667776d946596107e9)

Closes #2805

frontend/src/Settings/General/UpdateSettings.js

@@ -91,6 +91,7 @@ function UpdateSettings(props) {
                 type={inputTypes.CHECK}
                 name="updateAutomatically"
                 helpText={translate('UpdateAutomaticallyHelpText')}
+                helpTextWarning={updateMechanism.value === 'docker' ? translate('AutomaticUpdatesDisabledDocker', { appName: 'Readarr' }) : undefined}
                 onChange={onInputChange}
                 {...updateAutomatically}
               />

src/NzbDrone.Common/Extensions/PathExtensions.cs

@@ -140,7 +140,7 @@ namespace NzbDrone.Common.Extensions
 
         public static bool IsPathValid(this string path, PathValidationType validationType)
         {
-            if (path.ContainsInvalidPathChars() || string.IsNullOrWhiteSpace(path))
+            if (string.IsNullOrWhiteSpace(path) || path.ContainsInvalidPathChars())
             {
                 return false;
             }

src/NzbDrone.Core/Localization/Core/en.json

@@ -63,6 +63,7 @@
   "AutoUnmonitorPreviouslyDownloadedBooksHelpText": "Books deleted from disk are automatically unmonitored in Readarr",
   "Automatic": "Automatic",
   "AutomaticAdd": "Automatic Add",
+  "AutomaticUpdatesDisabledDocker": "Automatic updates are not directly supported when using the Docker update mechanism. You will need to update the container image outside of {appName} or use a script",
   "AutomaticallySwitchEdition": "Automatically Switch Edition",
   "Backup": "Backup",
   "BackupFolderHelpText": "Relative paths will be under Readarr's AppData directory",