disp: msm: sde: fix possible null pointer dereference

Fix a possible uninitialized variable usage in sde
catalog and a null pointer dereference in sde crtc.

Change-Id: I4299ade65fa7cf5bfc3d60d6d7a368d523286626
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>