Don't set defaultVersionCatalogFile if there's no version catalog

Fixes #698

Author: LouisCAD

plugins/core/src/main/kotlin/de/fayard/refreshVersions/core/RefreshVersionsCorePlugin.kt

@@ -25,8 +25,9 @@ open class RefreshVersionsCorePlugin : Plugin<Project> {
                 group = "refreshVersions"
                 description = "Search for new dependencies versions and update $versionsFileName"
                 if (shouldUpdateVersionCatalogs) {
-                    this.defaultVersionCatalog = VersionsCatalogs.getDefault(project)
-                    this.defaultVersionCatalogFile = project.file(VersionsCatalogs.LIBS_VERSIONS_TOML)
+                    this.defaultVersionCatalog = VersionsCatalogs.getDefault(project)?.also {
+                        this.defaultVersionCatalogFile = project.file(VersionsCatalogs.LIBS_VERSIONS_TOML)
+                    }
                 }
                 rootProjectSettingsFile = project.file("settings.gradle.kts").let { kotlinDslSettings ->
                     if (kotlinDslSettings.exists()) kotlinDslSettings else {

plugins/core/src/main/kotlin/de/fayard/refreshVersions/core/RefreshVersionsTask.kt

@@ -129,8 +129,7 @@ open class RefreshVersionsTask : DefaultTask() {
             if (versionPropertiesUpdated) OutputFile.VERSIONS_PROPERTIES.logFileWasModified()
 
             if (shouldUpdateVersionCatalogs) {
-                val libsToml = defaultVersionCatalogFile!!
-                if (libsToml.canRead()) {
+                defaultVersionCatalogFile?.let { libsToml ->
                     val updated = VersionsCatalogUpdater(
                         file = libsToml,
                         dependenciesUpdates = result.dependenciesUpdatesForVersionCatalog