Properly await future before checking their return code

src/main/kotlin/moe/kageru/kagebot/Kagebot.kt

@@ -26,7 +26,7 @@ class Kagebot {
             Globals.config.features.welcome!!.let { welcome ->
                 val message = event.user.sendMessage(welcome.embed)
                 // If the user disabled direct messages, try the fallback (if defined)
-                if (message.isCompletedExceptionally
+                if (!Util.wasSuccessful(message)
                     && welcome.fallbackChannel != null
                     && welcome.fallbackMessage != null
                 ) {

src/main/kotlin/moe/kageru/kagebot/Util.kt

@@ -6,6 +6,8 @@ import org.javacord.api.entity.channel.TextChannel
 import org.javacord.api.entity.message.MessageAuthor
 import org.javacord.api.entity.permission.Role
 import java.util.*
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.CompletionException
 
 object Util {
     inline fun <T> T.doIf(condition: (T) -> Boolean, op: (T) -> T): T {
@@ -47,6 +49,15 @@ object Util {
         }
     }
 
+    fun <T> wasSuccessful(future: CompletableFuture<T>): Boolean {
+        try {
+            future.join()
+        } catch (e: CompletionException) {
+            // we don’t care about this error, but I don’t want to spam stdout
+        }
+        return !future.isCompletedExceptionally
+    }
+
     @Throws(IllegalArgumentException::class)
     fun findChannel(idOrName: String): TextChannel {
         return when {

src/main/kotlin/moe/kageru/kagebot/command/MessageActions.kt

@@ -62,7 +62,7 @@ class Redirect(rawRedirect: RawRedirect) {
             }
         }
 
-        if (target.sendMessage(embed).isCompletedExceptionally) {
+        if (Util.wasSuccessful(target.sendMessage(embed))) {
             log.warning("Could not redirect message to channel $target")
         }
     }

src/main/resources/config.toml

@@ -13,7 +13,7 @@ messageDeleted = "Your message was deleted because it contained a banned word or
 # If no fallback channel or message is specified, no fallback will be sent.
 [feature.welcome]
 enabled = true
-fallbackChannel = 555097559023222825
+fallbackChannel = "555097559023222825"
 fallbackMessage = "@@ I would like to greet you, but I can’t. :("
 # This is a list of pairs where the key is the title and the value the content of the paragraph.
 # Do not use empty strings to get empty headings or paragraphs. The discord API rejects those.