Remove invalid assert from RenderActivity::setThread()

It is valid to call setThread() with null thread as part of activity
teardown, so the assert was invalid.

Change-Id: I0b3a89db1f5aff04c97def32b1881e0d66e5d250
diff --git a/framework/platform/android/tcuAndroidRenderActivity.cpp b/framework/platform/android/tcuAndroidRenderActivity.cpp
index 142435e..ddbf40e 100644
--- a/framework/platform/android/tcuAndroidRenderActivity.cpp
+++ b/framework/platform/android/tcuAndroidRenderActivity.cpp
@@ -291,7 +291,6 @@
 
 void RenderActivity::setThread (RenderThread* thread)
 {
-	DE_ASSERT(!m_thread && thread);
 	m_thread = thread;
 }