Don't throw exception when validating invalid paths

CHANGELOG.md

@@ -42,6 +42,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue where it was impossible to add or modify groups. [#7912](https://github.com/JabRef/jabref/pull/793://github.com/JabRef/jabref/pull/7921)
 - We fixed an issue where exported entries from a Citavi bib containing URLs could not be imported [#7892](https://github.com/JabRef/jabref/issues/7882)
 - We fixed an issue where the icons in the search bar had the same color, toggled as well as untoggled. [#8014](https://github.com/JabRef/jabref/pull/8014)
+- We fixed an issue where typing an invalid UNC path into the "Main file directory" text field caused an error. [#8107](https://github.com/JabRef/jabref/issues/8107)
 
 ### Removed
 

src/main/java/org/jabref/gui/preferences/linkedfiles/LinkedFilesTabViewModel.java

@@ -1,6 +1,7 @@
 package org.jabref.gui.preferences.linkedfiles;
 
 import java.nio.file.Files;
+import java.nio.file.InvalidPathException;
 import java.nio.file.Path;
 
 import javafx.beans.property.BooleanProperty;
@@ -55,8 +56,12 @@ public LinkedFilesTabViewModel(DialogService dialogService, PreferencesService p
         mainFileDirValidator = new FunctionBasedValidator<>(
                 mainFileDirectoryProperty,
                 input -> {
-                    Path path = Path.of(mainFileDirectoryProperty.getValue());
-                    return (Files.exists(path) && Files.isDirectory(path));
+                    try {
+                        Path path = Path.of(mainFileDirectoryProperty.getValue());
+                        return (Files.exists(path) && Files.isDirectory(path));
+                    } catch (InvalidPathException ex) {
+                        return false;
+                    }
                 },
                 ValidationMessage.error(String.format("%s > %s > %s %n %n %s",
                         Localization.lang("File"),