struct declaration missing when struct used as ubo arg has struct slot but not used in body

[cbaggers]

No type ref so it's stripped, however it causes an error.

Error compiling fragment-shader: 
0(17) : error C0000: syntax error, unexpected '[', expecting "::" at token "["


// fragment-stage
#version 450

in _FROM_GEOMETRY_STAGE_
{
     in vec2 _GEOMETRY_STAGE_OUT_0;
} v_in;

layout(location = 0)  out vec4 _FRAGMENT_STAGE_OUT_0;

uniform sampler2D MSDF;
uniform float PX_RANGE;
uniform vec4 BG_COLOR;
uniform vec4 FG_COLOR;
layout(std140) uniform _UBO_ATLAS
{
    BITMAP_GLYPH[500] GLYPHS;
} ATLAS;

float MEDIAN(float R, float G, float B);

float MEDIAN(float R, float G, float B)
{
    return max(min(R,G),min(max(R,G),B));
}

void main()
{
    vec2 POS = vec2(v_in._GEOMETRY_STAGE_OUT_0.x,(float(1) - v_in._GEOMETRY_STAGE_OUT_0.y));
    vec3 SAM = texture(MSDF,POS).xyz;
    ivec2 SIZE4 = textureSize(MSDF,0);
    vec2 MSDF_UNIT = (PX_RANGE / vec2(float(SIZE4.x),float(SIZE4.y)));
    float SIG_DIST = (MEDIAN(SAM.x,SAM.y,SAM.z) - 0.5f);
    SIG_DIST *= dot(MSDF_UNIT,(0.5f / fwidth(POS)));
    float OPACITY = clamp((SIG_DIST + 0.5f),0.0f,1.0f);
    vec4 g_GEXPR0_4913 = mix(BG_COLOR,FG_COLOR,OPACITY);
    _FRAGMENT_STAGE_OUT_0 = g_GEXPR0_4913;
    return;
}
   [Condition of type SIMPLE-ERROR]