Made sure that AbstractFifo::getFreeSpace returns the correct amount.

modules/juce_core/containers/juce_AbstractFifo.cpp

@@ -35,7 +35,7 @@ AbstractFifo::AbstractFifo (const int capacity) noexcept
 AbstractFifo::~AbstractFifo() {}
 
 int AbstractFifo::getTotalSize() const noexcept           { return bufferSize; }
-int AbstractFifo::getFreeSpace() const noexcept           { return bufferSize - getNumReady(); }
+int AbstractFifo::getFreeSpace() const noexcept           { return bufferSize - getNumReady() - 1; }
 
 int AbstractFifo::getNumReady() const noexcept
 {