glvdebug: Close currently open trace files before trying to open a new one.
glvdebug: Close currently open trace files before trying to open a new one.

* Previously, If the user used File->Open to open a new trace file, the currently open trace file would not be closed. This was resulting in multiple Replayer tabs being visible in the UI (and likely a bunch of other less noticeable issues).
* Attempting to close the trace file prior to opening a new one seems the best way to resolve this issue.

KhronosGroup/Vulkan-LoaderAndValidationLayers,sashinde/VulkanTools,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,critsec/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,critsec/Vulkan-LoaderAndValidationLayers,Radamanthe/VulkanSamples,sashinde/VulkanTools,Radamanthe/VulkanSamples,Radamanthe/VulkanSamples,sashinde/VulkanTools,sashinde/VulkanTools,KhronosGroup/Vulkan-LoaderAndValidationLayers,Radamanthe/VulkanSamples,KhronosGroup/Vulkan-LoaderAndValidationLayers,critsec/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,elongbug/Vulkan-LoaderAndValidationLayers,critsec/Vulkan-LoaderAndValidationLayers