Throw error if creation of buffered audio source fails.

This can happen if we're out of audio streams. Before, we just kinda pretended like everything was OK, which easily caused crash bugs in e.g. MIDI.

Ideally the audio engine would be less terrible and this could be handled better than "throw new Exception()", but I'm fixing a stack overflow here alright?

RELEASE-NOTES.md

@@ -43,7 +43,7 @@ END TEMPLATE-->
 
 ### Bugfixes
 
-*None yet*
+* Fixed potential crashes if buffered audio sources (e.g. MIDI) fail to create due to running out of audio streams.
 
 ### Other
 

Robust.Client/Graphics/Audio/ClydeAudio.cs

@@ -261,6 +261,9 @@ namespace Robust.Client.Graphics.Audio
         {
             var source = AL.GenSource();
 
+            if (!AL.IsSource(source))
+                throw new Exception("Failed to generate source. Too many simultaneous audio streams?");
+
             // ReSharper disable once PossibleInvalidOperationException
 
             var audioSource = new BufferedAudioSource(this, source, AL.GenBuffers(buffers), floatAudio);