sw/xlib: NULL-out pointers after freeing image data
sw/xlib: NULL-out pointers after freeing image data

This fixes a double-free() error when not using a shared memory XImage.
The XDestroyImage() function frees the ximage->data buffer if non-NULL.
If we free it ourselves, we also need to NULL-out the pointer.

KTXSoftware/glsl2agal,mapbox/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,zz85/glsl-optimizer,bkaradzic/glsl-optimizer,dellis1972/glsl-optimizer,zeux/glsl-optimizer,zz85/glsl-optimizer,zz85/glsl-optimizer,metora/MesaGLSLCompiler,adobe/glsl2agal,metora/MesaGLSLCompiler,mcanthony/glsl-optimizer,adobe/glsl2agal,zeux/glsl-optimizer,adobe/glsl2agal,bkaradzic/glsl-optimizer,dellis1972/glsl-optimizer,mcanthony/glsl-optimizer,mcanthony/glsl-optimizer,tokyovigilante/glsl-optimizer,zeux/glsl-optimizer,dellis1972/glsl-optimizer,djreep81/glsl-optimizer,adobe/glsl2agal,benaadams/glsl-optimizer,KTXSoftware/glsl2agal,benaadams/glsl-optimizer,zz85/glsl-optimizer,tokyovigilante/glsl-optimizer,dellis1972/glsl-optimizer,wolf96/glsl-optimizer,benaadams/glsl-optimizer,benaadams/glsl-optimizer,benaadams/glsl-optimizer,mapbox/glsl-optimizer,jbarczak/glsl-optimizer,djreep81/glsl-optimizer,bkaradzic/glsl-optimizer,zeux/glsl-optimizer,jbarczak/glsl-optimizer,bkaradzic/glsl-optimizer,mapbox/glsl-optimizer,benaadams/glsl-optimizer,metora/MesaGLSLCompiler,jbarczak/glsl-optimizer,mcanthony/glsl-optimizer,KTXSoftware/glsl2agal,djreep81/glsl-optimizer,wolf96/glsl-optimizer,mapbox/glsl-optimizer,wolf96/glsl-optimizer,wolf96/glsl-optimizer,dellis1972/glsl-optimizer,mcanthony/glsl-optimizer,KTXSoftware/glsl2agal,KTXSoftware/glsl2agal,adobe/glsl2agal,djreep81/glsl-optimizer,wolf96/glsl-optimizer,bkaradzic/glsl-optimizer,tokyovigilante/glsl-optimizer,zeux/glsl-optimizer,tokyovigilante/glsl-optimizer,tokyovigilante/glsl-optimizer,mapbox/glsl-optimizer,zz85/glsl-optimizer,djreep81/glsl-optimizer,jbarczak/glsl-optimizer