render: use cell cols from compose chain, not grapheme

fcft’s view of how many columns a grapheme cluster is may differ from
our own. Make sure the rendered glyph matches the number of columns
that were allocated when the cluster was printed.

render.c

@@ -570,10 +570,11 @@ render_cell(struct terminal *term, pixman_image_t *pix,
             }
 
             if (grapheme != NULL) {
+                cell_cols = composed->width;
+
                 composed = NULL;
                 glyphs = grapheme->glyphs;
                 glyph_count = grapheme->count;
-                cell_cols = grapheme->cols;
             }
         }