Sampler object fix

The code was not allowing to unset a sampler object from a texture,
so the faulty condition was removed to fix the issue.

Fixes 30 tests in:
dEQP.functional.samplers.*

Change-Id: Ibbc3389d3d6135db7bc5a2f87f0df5527b78c7fd
Reviewed-on: https://swiftshader-review.googlesource.com/7360
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
diff --git a/src/OpenGL/libGLESv2/Context.cpp b/src/OpenGL/libGLESv2/Context.cpp
index 39374ce..af5c95a 100644
--- a/src/OpenGL/libGLESv2/Context.cpp
+++ b/src/OpenGL/libGLESv2/Context.cpp
@@ -1284,10 +1284,7 @@
 
 	Sampler* samplerObject = getSampler(sampler);
 
-	if(sampler)
-	{
-		mState.sampler[unit] = samplerObject;
-	}
+	mState.sampler[unit] = samplerObject;
 
 	return !!samplerObject;
 }