Whiskermenu gtk3 (v.2) cannot be resized

[Strategos]

After introduction of whiskermenu gtk3 (v.2) it is impossible to resize the menu from the resize corner.
When I switch to xfwm4, then it is possible to resize as usual.

with packages

```
compiz-manjaro 0.9.13.1.r4138-5
xfce4-whiskermenu-plugin 2.1.6-1
gtk2 2.24.32-1
gtk3 3.22.29+86+gd92df4ff2c-1

```

inxi -SGIfxxxz

```
System: Host: ma64testimg Kernel: 4.14.34-1-MANJARO x86_64 bits: 64 compiler: gcc v: 7.3.1
           Desktop: Xfce 4.12.4 (Gtk 2.24.31) info: xfce4-panel,org.gnome.chrome_gnome_shell.json
           dm: lightdm 1.26.0 Distro: Manjaro Linux 17.1.8 Hakoila
CPU: Topology: Dual Core model: Intel Core i3 560 type: MT MCP arch: Nehalem rev: 5 L2 cache: 4096 KiB
           bogomips: 26772
           Speed: 1204 MHz min/max: 1200/3333 MHz Core speeds (MHz): 1: 1204 2: 1204 3: 1204 4: 1204
           Flags: acpi aperfmperf apic arat arch_perfmon bts clflush cmov constant_tsc cpuid cx16 cx8 de ds_cpl
           dtes64 dtherm dts ept est flexpriority fpu fxsr ht lahf_lm lm mca mce mmx monitor msr mtrr
           nonstop_tsc nopl nx pae pat pbe pcid pdcm pebs pge pni popcnt pse pse36 pti rdtscp rep_good sep ss
           sse sse2 sse4_1 sse4_2 ssse3 syscall tm tm2 tpr_shadow tsc vme vmx vnmi vpid xtopology xtpr
Graphics: Card-1: NVIDIA GF116 [GeForce GTX 550 Ti] driver: nvidia v: 390.48 bus ID: 01:00.0
           chip ID: 10de:1244
           Display Server: x11 (X.Org 1.19.6) driver: nvidia compositor: compiz
           resolution: 1920x1080~60Hz, 1920x1080~60Hz
           OpenGL: renderer: GeForce GTX 550 Ti/PCIe/SSE2 v: 4.6.0 NVIDIA 390.48 direct render: Yes
Info: Processes: 215 Uptime: 44m Memory: 7.72 GiB used: 4.17 GiB (54.0%) Init: systemd v: 238 Compilers:
           gcc: 7.3.1 alt: 6 Shell: bash v: 4.4.19 running in: xfce4-terminal inxi: 3.0.00

```

coredump

```
systemd-coredump[6804]: Process 918 (compiz) of user 1000 dumped core.

                                                       Stack trace of thread 918:
                                                       #0 0x00007fd7c1caf860 raise (libc.so.6)
                                                       #1 0x00007fd7c1cb0ec9 abort (libc.so.6)
                                                       #2 0x00007fd7c1cf2437 __libc_message (libc.so.6)
                                                       #3 0x00007fd7c1cf878b malloc_printerr (libc.so.6)
                                                       #4 0x00007fd7c1cfa4fc _int_free (libc.so.6)
                                                       #5 0x00007fd7c155ac65 XDestroyRegion (libX11.so.6)
                                                       #6 0x00007fd7c1cb27b2 __cxa_finalize (libc.so.6)
                                                       #7 0x00007fd7c261f6e4 n/a (libcompiz_core.so.ABI-20170630)
                                                       #8 0x00007fd7c28d4af3 _dl_fini (ld-linux-x86-64.so.2)
                                                       #9 0x00007fd7c1cb2448 __run_exit_handlers (libc.so.6)
                                                       #10 0x00007fd7c1cb249a exit (libc.so.6)
                                                       #11 0x00007fd7c2671a18 n/a (libcompiz_core.so.ABI-20170630)
                                                       #12 0x00007fd7c0ae1477 _SmcProcessMessage (libSM.so.6)
                                                       #13 0x00007fd7c0cf5feb IceProcessMessages (libICE.so.6)
                                                       #14 0x00007fd7c26714be n/a (libcompiz_core.so.ABI-20170630)
                                                       #15 0x00007fd7c262c9ee _ZN11CompWatchFd16internalCallbackEN4Glib11IOConditionE (libcompiz_core.so.ABI-20170630)
                                                       #16 0x00007fd7c08b37ec _ZN4Glib8IOSource8dispatchEPN4sigc9slot_baseE (libglibmm-2.4.so.1)
                                                       #17 0x00007fd7c08b3a0f _ZN4Glib6Source14dispatch_vfuncEP8_GSourcePFiPvES3_ (libglibmm-2.4.so.1)
                                                       #18 0x00007fd7c05921d6 g_main_context_dispatch (libglib-2.0.so.0)
                                                       #19 0x00007fd7c05925b1 n/a (libglib-2.0.so.0)
                                                       #20 0x00007fd7c05928e2 g_main_loop_run (libglib-2.0.so.0)
                                                       #21 0x00007fd7c2625528 _ZN6compiz14private_screen12EventManager14startEventLoopEP9_XDisplay (libcompiz_core.so.ABI-20>
                                                       #22 0x000055b479218639 main (compiz)
                                                       #23 0x00007fd7c1c9bf4a __libc_start_main (libc.so.6)
                                                       #24 0x000055b47921869a _start (compiz)

                                                       Stack trace of thread 928:
                                                       #0 0x00007fd7c1d6697b __poll (libc.so.6)
                                                       #1 0x00007fd7c0592523 n/a (libglib-2.0.so.0)
                                                       #2 0x00007fd7c059263e g_main_context_iteration (libglib-2.0.so.0)
                                                       #3 0x00007fd7c0592692 n/a (libglib-2.0.so.0)
                                                       #4 0x00007fd7c05baa2a n/a (libglib-2.0.so.0)
                                                       #5 0x00007fd7bff1e08c start_thread (libpthread.so.0)
                                                       #6 0x00007fd7c1d70e7f __clone (libc.so.6)

```