Do not modify the argument to exec_command
Do not modify the argument to exec_command

This fixes a segfault when using the ZQ key binding as reported
by Silvan Jegen.

trengrj/vis,8l/vis,twinshadow/vis,cpehle/vis,8l/vis,clehner/vis,clehner/vis,rychipman/vis,twinshadow/vis,trengrj/vis,cpehle/vis,rychipman/vis