ref_gl: vbo: do not do zero-length drawcalls (fix glError on vivante)

ref/gl/gl_rsurf.c

@@ -2389,6 +2389,9 @@ draw details when not enough tmus
 */
 static void R_AdditionalPasses( vboarray_t *vbo, int indexlen, void *indexarray, texture_t *tex, qboolean resetvbo, size_t offset )
 {
+	if( !indexlen )
+		return;
+
 	// draw details in additional pass
 	if( r_detailtextures.value && r_vbo_detail.value == 1 && mtst.tmu_dt == -1 && tex->dt_texturenum )
 	{
@@ -2773,6 +2776,8 @@ Draw array for given vbotexture_t. build and draw dynamic lightmaps if present
 */
 static void R_DrawLightmappedVBO( vboarray_t *vbo, vbotexture_t *vbotex, texture_t *texture, int lightmap, qboolean skiplighting )
 {
+	if( vbotex->curindex )
+	{
 #if !defined XASH_NANOGL || defined XASH_WES && XASH_EMSCRIPTEN // WebGL need to know array sizes
 		if( pglDrawRangeElements )
 			pglDrawRangeElements( GL_TRIANGLES, 0, vbo->array_len, vbotex->curindex, GL_VBOINDEX_TYPE, vbotex->indexarray );
@@ -2800,6 +2805,8 @@ static void R_DrawLightmappedVBO( vboarray_t *vbo, vbotexture_t *vbotex, texture
 			pglEnable( GL_TEXTURE_2D );
 			R_SetDecalMode( false );
 		}
+	}
+
 	//Msg( "%d %d %d\n", vbo->array_len, vbotex->len, lightmap );
 	if( skiplighting )
 	{