`dot` crashed in environments without installed fonts (typical case for hasher).

How to reproduce:
```
echo 'digraph { a -> b }' | dot -vvv -Tsvg > output.svg
```

Actual output:
```
Starting program: /usr/bin/dot test -Tsvg -vvv
warning: Error disabling address space randomization: Operation not permitted
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
dot - graphviz version 2.43.0 (0)
libdir = "/usr/lib64/graphviz"
Activated plugin library: libgvplugin_core.so.6
Using render: svg:core
Using device: svg:svg:core
Activated plugin library: libgvplugin_dot_layout.so.6
Using layout: dot:dot_layout
The plugin configuration file:
        /usr/lib64/graphviz/config6
                was successfully loaded.
    render      :  cairo dot dot_json fig gd json json0 lasi map mp pic pov ps svg tk visio vml vrml xdot xdot_json
    layout      :  circo dot fdp neato nop nop1 nop2 osage patchwork sfdp twopi
    textlayout  :  textlayout
    device      :  bmp canon cmap cmapx cmapx_np dot dot_json eps fig gd gd2 gif gtk gv ico imap imap_np ismap jpe jpeg jpg json json0 mp pdf pic plain plain-ext png pov ps ps2 svg svgz tif tiff tk vdx vml vmlz vrml wbmp x11 xdot xdot1.2 xdot1.4 xdot_json xlib
    loadimage   :  (lib) bmp eps gd gd2 gif ico jpe jpeg jpg png ps svg xbm
pack info:
  mode   undefined
  size   0
  flags  0
  margin 8
pack info:
  mode   node
  size   0
  flags  0
...


(process:998): Pango-CRITICAL **: 09:31:30.427: pango_font_describe: assertion 'font != NULL' failed

(process:998): Pango-CRITICAL **: 09:31:30.428: pango_font_description_get_variant: assertion 'desc != NULL' failed

(process:998): Pango-CRITICAL **: 09:31:30.428: pango_font_get_hb_font: assertion 'PANGO_IS_FONT (font)' failed

Thread 1 "dot" received signal SIGSEGV, Segmentation fault.
0x00007f642a9138f7 in hb_ot_layout_get_baseline (font=font@entry=0x0, baseline_tag=baseline_tag@entry=HB_OT_LAYOUT_BASELINE_TAG_ROMAN, direction=direction@entry=HB_DIRECTION_LTR, script_tag=script_tag@entry=1818326126, language_tag=language_tag@entry=0, coord=coord@entry=0x7ffe81087290) at ../src/hb-ot-layout.cc:2063
Python Exception <class 'UnicodeEncodeError'>: 'ascii' codec can't encode character '\xa9' in position 37: ordinal not in range(128)
2063      return font->face->table.BASE->get_baseline (font, baseline_tag, direction, script_tag, language_tag, coord);

```

This worked (and works) just fine with `libpango-1.48.11-alt1.x86_64.rpm`, but was broken with `libpango-1.50.5-alt1.x86_64.rpm`.

see https://gitlab.gnome.org/GNOME/pango/-/commit/539ca68c7725f9d7bfb6ba8ad3c94f354a6c1142

This commit makes `fonts-` mandatory.