Showing exception type for exceptions without message

Before, the content area of the message box would be empty for these exceptions.

VERSION.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* More helpful error dialogs for internal errors in Rhubarb Lip Sync for Spine 
 * Internal errors in Rhubarb Lip Sync for Spine are logged to stderr
 
 ## Version 1.7.0

extras/EsotericSoftwareSpine/src/main/kotlin/com/rhubarb_lip_sync/rhubarb_for_spine/AudioFileModel.kt

@@ -167,7 +167,11 @@ class AudioFileModel(
 				Platform.runLater {
 					Alert(Alert.AlertType.ERROR).apply {
 						headerText = "Error performing lip sync for event '$eventName'."
-						contentText = e.message
+						contentText = if (e.message.isNullOrEmpty())
+							// Some exceptions don't have a message
+							"An internal error of type ${e.javaClass.name} occurred."
+						else
+							e.message
 						show()
 					}
 				}