ImportError: libqt_gui_cpp.so: cannot open shared object file: No such file or directory

I have two issue

issue 1-)

i get the following error when the first line of /opt/ros/melodic/rosrun is this #!/usr/bin/env bash, rviz does not working

$ rosrun rviz rviz

/opt/ros/melodic/lib/rviz/rviz: error while loading shared libraries: librviz.so: cannot open shared object file: No such file or directory

#! /bin/bash instead of #!/usr/bin/env bash, so problem solved, Why?

issue 2-) I get the following error when I run rosrun rqt_gui rqt_gui or another all rqt programs

Could not import "pyqt" bindings of qt_gui_cpp library - so C++ plugins will not be available:
Traceback (most recent call last):
  File "/opt/ros/melodic/lib/python2.7/dist-packages/qt_gui_cpp/cpp_binding_helper.py", line 43, in <module>
    from . import libqt_gui_cpp_sip
ImportError: libqt_gui_cpp.so: cannot open shared object file: No such file or directory

But the rqt_gui program is working properly as far as I can see.

Informations:

$ echo $LD_LIBRARY_PATH
/home/harun/catkin_ws/devel/lib:/opt/ros/melodic/lib:/usr/lib/x86_64-linux-gnu

$ env | grep LD
nothing

LD_LIBRARY_PATH is set but why is LD_LIBRARY_PATH not in env? is it normal?

I tried the commands in this link rqt_graph pyqt binding of qt_gui_cpp library but problem is not solved

Could this issue be related to the situation in first issue? how can i solve this situation?