Don't end up killing init if process selected to be killed terminates before...

Don't end up killing init if process selected to be killed terminates before the user selects a signal. Closes #3606072.

ScreenManager.c

@@ -173,7 +173,8 @@ void ScreenManager_run(ScreenManager* this, Panel** lastFocus, int* lastKey) {
                for (int i = 0; i < this->panelCount; i++) {
                   Panel* panel = (Panel*) Vector_get(this->panels, i);
                   if (mevent.x > panel->x && mevent.x <= panel->x+panel->w &&
-                     mevent.y > panel->y && mevent.y <= panel->y+panel->h) {
+                     mevent.y > panel->y && mevent.y <= panel->y+panel->h &&
+                     (this->allowFocusChange || panelFocus == panel) ) {
                      focus = i;
                      panelFocus = panel;
                      Panel_setSelected(panel, mevent.y - panel->y + panel->scrollV - 1);

htop.c

@@ -217,9 +217,10 @@ static Object* pickFromVector(Panel* panel, Panel* list, int x, int y, const cha
    Panel* panelFocus;
    int ch;
    bool unfollow = false;
+   Process* p = (Process*)Panel_getSelected(panel);
+   int pid = p ? p->pid : -1;
    if (header->pl->following == -1) {
-      Process* p = (Process*)Panel_getSelected(panel);
-      header->pl->following = p ? p->pid : -1;
+      header->pl->following = pid;
       unfollow = true;
    }
    ScreenManager_run(scr, &panelFocus, &ch);
@@ -231,7 +232,11 @@ static Object* pickFromVector(Panel* panel, Panel* list, int x, int y, const cha
    Panel_resize(panel, COLS, LINES-y-1);
    FunctionBar_draw(prevBar, NULL);
    if (panelFocus == list && ch == 13) {
-      return Panel_getSelected(list);
+      Process* selected = (Process*)Panel_getSelected(panel);
+      if (selected->pid == pid)
+         return Panel_getSelected(list);
+      else
+         beep();
    }
    return NULL;
 }