Merged revision(s) 21556 from trunk/OpenMPT:

[Fix] Avoid crash in plugin bridge if plugin changes channel configuration without telling us (observed with Surge XT via vst3ishell, https://bugs.openmpt.org/view.php?id=1807).
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git-svn-id: https://source.openmpt.org/svn/openmpt/branches/OpenMPT-1.31@21557 56274372-70c3-4bfc-bfc3-4c3a0b034d27

pluginBridge/Bridge.cpp

@@ -478,6 +478,9 @@ void PluginBridge::DispatchToPlugin(DispatchMsg &msg)
 		// [value]: 0 means "turn off", 1 means "turn on"
 		::SetThreadPriority(m_audioThread, msg.value ? THREAD_PRIORITY_ABOVE_NORMAL : THREAD_PRIORITY_NORMAL);
 		m_sharedMem->tailSize = static_cast<int32>(Dispatch(effGetTailSize, 0, 0, nullptr, 0.0f));
+		// Plugin should tell us if number of channels changes through audioMasterIOChanged, but Surge XT via vst3ishell has been observed not to do that.
+		if(msg.value)
+			DispatchToHost(audioMasterVendorSpecific, kVendorOpenMPT, kUpdateProcessingBuffer, nullptr, 0.0f);
 		break;
 
 	case effEditGetRect: