POSIX: Set fileHandle to 0 after closing in MemoryMappedFile::openInternal() to prevent it from being closed again in the destructor

modules/juce_core/native/juce_posix_SharedCode.h

@@ -578,6 +578,7 @@ void MemoryMappedFile::openInternal (const File& file, AccessMode mode, bool exc
         }
 
         close (fileHandle);
+        fileHandle = 0;
     }
 }