msm: kgsl: Ensure context pointer exists before dereferencing

When trying to add commands to the ringbuffer command stream, ensure
that the context point is not NULL before dereferencing it.

Change-Id: I6d8217ed4b180454eb43f2db161c10e86bc207da
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>
diff --git a/drivers/gpu/msm/adreno_ringbuffer.c b/drivers/gpu/msm/adreno_ringbuffer.c
index 9d0d0ae..2a35556 100644
--- a/drivers/gpu/msm/adreno_ringbuffer.c
+++ b/drivers/gpu/msm/adreno_ringbuffer.c
@@ -545,7 +545,7 @@
 	if (context && context->flags & CTXT_FLAGS_PER_CONTEXT_TS)
 		context_id = context->id;
 
-	if ((context->flags & CTXT_FLAGS_USER_GENERATED_TS) &&
+	if ((context && context->flags & CTXT_FLAGS_USER_GENERATED_TS) &&
 			(!(flags & KGSL_CMD_FLAGS_INTERNAL_ISSUE))) {
 		if (timestamp_cmp(rb->timestamp[context_id],
 						timestamp) >= 0) {