Added an assertion to check the OpenGL swap interval on MacOS

modules/juce_core/containers/juce_AbstractFifo.h

@@ -331,7 +331,7 @@ inline void AbstractFifo::ScopedReadWrite<AbstractFifo::ReadOrWrite::write>::fin
 {
     f.finishedWrite (num);
 }
-    
+
 template<>
 inline void AbstractFifo::ScopedReadWrite<AbstractFifo::ReadOrWrite::read>::prepare (AbstractFifo& f, int num) noexcept
 {

modules/juce_opengl/native/juce_OpenGL_osx.h

@@ -200,6 +200,10 @@ public:
 
     bool setSwapInterval (int numFramesPerSwap)
     {
+        // The macOS OpenGL programming guide says that numFramesPerSwap
+        // can only be 0 or 1.
+        jassert (isPositiveAndBelow (numFramesPerSwap, 2));
+
         minSwapTimeMs = (numFramesPerSwap * 1000) / 60;
 
         [renderContext setValues: (const GLint*) &numFramesPerSwap