check for valid block binding in parseUniformBlocks

src/shader.cpp

@@ -625,6 +625,7 @@ parseUniformBlocks(MemoryArena* arena, ShaderProgram* s, GLContext* gl_ctx)
 
 		ub.binding_idx = ctxGetUniformBlockBinding(gl_ctx, ub.name);
 
+		assert(ub.binding_idx >= 0);
 #if 0
 		if (ub.binding_idx < 0)
 			return false;