Only use an extra draw call for the background when drawing interleaved cells if it is actually required

kitty/gl.c

@@ -126,6 +126,12 @@ init_uniforms(int program) {
     }
 }
 
+GLint
+get_uniform_location(int program, const char *name) {
+    Program *p = programs + program;
+    return glGetUniformLocation(p->id, name);
+}
+
 GLint
 get_uniform_information(int program, const char *name, GLenum information_type) {
     GLint q; GLuint t;