Unbinding uniform buffers on context shutdown.
Fixes bug swiftshader:72.

Change-Id: I4fcc6c47ec8561150c88fea200aeb6baf9534c00
Reviewed-on: https://swiftshader-review.googlesource.com/10511
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Ben Vanik <benvanik@google.com>
diff --git a/src/OpenGL/libGLESv2/Context.cpp b/src/OpenGL/libGLESv2/Context.cpp
index 84196ac..dbb5cf2 100644
--- a/src/OpenGL/libGLESv2/Context.cpp
+++ b/src/OpenGL/libGLESv2/Context.cpp
@@ -245,6 +245,11 @@
 	mState.pixelPackBuffer = nullptr;
 	mState.pixelUnpackBuffer = nullptr;
 	mState.genericUniformBuffer = nullptr;
+
+	for(int i = 0; i < MAX_UNIFORM_BUFFER_BINDINGS; i++) {
+		mState.uniformBuffers[i].set(nullptr, 0, 0);
+	}
+
 	mState.renderbuffer = nullptr;
 
 	for(int i = 0; i < MAX_COMBINED_TEXTURE_IMAGE_UNITS; ++i)