Fix CLAP plugins under hosts without latency callbacks

Closes #432

Signed-off-by: falkTX <falktx@falktx.com>

distrho/src/DistrhoPluginCLAP.cpp

@@ -1375,6 +1375,9 @@ public:
 
         fLastKnownLatency = latency;
 
+        if (fHostExtensions.latency == nullptr)
+            return;
+
         if (isActive)
         {
             fLatencyChanged = true;