rqt_graph error

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Hello, I am using Arch Linux and I installed ros-melodic-desktop-full. However when I try to run rqt_graph i have the following errors.

$ rosrun rqt_graph rqt_graph
QApplication: invalid style override passed, ignoring it.
    Available styles: dsemilight, dsemidark, dlight, ddark, Windows, Fusion
"dot" with args ['-Tdot', '/tmp/tmpylxzm6lx'] returned code: 1

stdout, stderr:
 b''
b'Error: /usr/lib/graphviz/config6 is zero sized, or other read error.\nFormat: "dot" not recognized. Use one of:\n'

PluginHandlerDirect._restore_settings() plugin "rqt_graph/RosGraph#0" raised an exception:
Traceback (most recent call last):
  File "/opt/ros/melodic/lib/python3.7/site-packages/qt_gui/plugin_handler_direct.py", line 116, in _restore_settings
    self._plugin.restore_settings(plugin_settings_plugin, instance_settings_plugin)
  File "/opt/ros/melodic/lib/python3.7/site-packages/rqt_graph/ros_graph.py", line 217, in restore_settings
    self._refresh_rosgraph()
  File "/opt/ros/melodic/lib/python3.7/site-packages/rqt_graph/ros_graph.py", line 246, in _refresh_rosgraph
    self._update_graph_view(self._generate_dotcode())
  File "/opt/ros/melodic/lib/python3.7/site-packages/rqt_graph/ros_graph.py", line 280, in _generate_dotcode
    hide_dynamic_reconfigure=hide_dynamic_reconfigure)
  File "/opt/ros/melodic/lib/python3.7/site-packages/rqt_graph/dotcode.py", line 877, in generate_dotcode
    dotcode = dotcode_factory.create_dot(dotgraph)
  File "/opt/ros/melodic/lib/python3.7/site-packages/qt_dotgraph/pydotfactory.py", line 168, in create_dot
    dot = graph.create_dot()
  File "/usr/lib/python3.7/site-packages/pydot.py", line 1723, in new_method
    format=f, prog=prog, encoding=encoding)
  File "/usr/lib/python3.7/site-packages/pydot.py", line 1945, in create
    assert process.returncode == 0, process.returncode
AssertionError: 1

"dot" with args ['-Tdot', '/tmp/tmp84jgo2t0'] returned code: 1

stdout, stderr:
 b''
b'Error: /usr/lib/graphviz/config6 is zero sized, or other read error.\nFormat: "dot" not recognized. Use one of:\n'

Traceback (most recent call last):
  File "/opt/ros/melodic/lib/python3.7/site-packages/rqt_graph/ros_graph.py", line 246, in _refresh_rosgraph
    self._update_graph_view(self._generate_dotcode())
  File "/opt/ros/melodic/lib/python3.7/site-packages/rqt_graph/ros_graph.py", line 280, in _generate_dotcode
    hide_dynamic_reconfigure=hide_dynamic_reconfigure)
  File "/opt/ros/melodic/lib/python3.7/site-packages/rqt_graph/dotcode.py", line 877, in generate_dotcode
    dotcode = dotcode_factory.create_dot(dotgraph)
  File "/opt/ros/melodic/lib/python3.7/site-packages/qt_dotgraph/pydotfactory.py", line 168, in create_dot
    dot = graph.create_dot()
  File "/usr/lib/python3.7/site-packages/pydot.py", line 1723, in new_method
    format=f, prog=prog, encoding=encoding)
  File "/usr/lib/python3.7/site-packages/pydot.py", line 1945, in create
    assert process.returncode == 0, process.returncode
AssertionError: 1
Aborted (core dumped)

Has anyone any idea what's going wrong? Other rqt_* commands runs fine.