chore: more luacheck fixes

.ci/script.sh

@@ -8,4 +8,4 @@ make all
 make testfront
 set +o pipefail
 luajit $(which luacheck) --no-color -q frontend | tee ./luacheck.out
-test $(grep Total ./luacheck.out | awk '{print $2}') -le 19
+test $(grep Total ./luacheck.out | awk '{print $2}') -le 17

frontend/apps/reader/modules/readerpaging.lua

@@ -707,15 +707,13 @@ function ReaderPaging:onGotoPageRel(diff)
     local new_va = self.visible_area:copy()
     local x_pan_off, y_pan_off = 0, 0
 
-    if self.zoom_mode == "free" then
-        -- do nothing in free zoom mode
-    elseif self.zoom_mode:find("width") then
+    if self.zoom_mode:find("width") then
         y_pan_off = self.visible_area.h * diff
     elseif self.zoom_mode:find("height") then
         -- negative x panning if writing direction is right to left
         local direction = self.ui.document.configurable.writing_direction
         x_pan_off = self.visible_area.w * diff * (direction == 1 and -1 or 1)
-    else
+    elseif self.zoom_mode ~= "free" then  -- do nothing in "free" zoom mode
         -- must be fit content or page zoom mode
         if self.visible_area.w == self.page_area.w then
             y_pan_off = self.visible_area.h * diff

frontend/device/gesturedetector.lua

@@ -160,8 +160,7 @@ function GestureDetector:getPath(slot)
     local y_diff = self.last_tevs[slot].y - self.first_tevs[slot].y
     local direction = nil
     local distance = math.sqrt(x_diff*x_diff + y_diff*y_diff)
-    if x_diff == 0 and y_diff == 0 then
-    else
+    if x_diff ~= 0 or y_diff ~= 0 then
         local v_direction = y_diff < 0 and "north" or "south"
         local h_direction = x_diff < 0 and "west" or "east"
         if math.abs(y_diff) > 0.577*math.abs(x_diff)