dt_ctl_set_display_profile(): free icc buffer we just got if profile has not changed

Fixes following LeakSanitizer-detected leak:
Direct leak of 1548384 byte(s) in 3 object(s) allocated from:
    #0 0x7f913367474f in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.1+0x5474f)
    #1 0x7f9130c67799 in g_malloc (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x4f799)
    #2 0x7f91325abb85 (/usr/lib/x86_64-linux-gnu/libgdk-3.so.0+0x53b85)
    #3 0x7f9133274b15 in dt_ctl_set_display_profile /home/lebedevri/darktable/src/control/control.c:199
    #4 0x7f9133391d6e in window_configure /home/lebedevri/darktable/src/gui/gtk.c:625
    #5 0x7f9132a0531c (/usr/lib/x86_64-linux-gnu/libgtk-3.so.0+0x1ed31c)
    #6 0x7f9130f382d4 in g_closure_invoke (/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0+0x102d4)
    #7 0x7f9130f4a03b (/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0+0x2203b)
    #8 0x7f9130f521a4 in g_signal_emit_valist (/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0+0x2a1a4)
    #9 0x7f9130f528fe in g_signal_emit (/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0+0x2a8fe)
    #10 0x7f9132b35de3 (/usr/lib/x86_64-linux-gnu/libgtk-3.so.0+0x31dde3)
    #11 0x7f9132a04819 in gtk_main_do_event (/usr/lib/x86_64-linux-gnu/libgtk-3.so.0+0x1ec819)
    #12 0x7f91325a7b11 (/usr/lib/x86_64-linux-gnu/libgdk-3.so.0+0x4fb11)
    #13 0x7f9130c61c3c in g_main_context_dispatch (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x49c3c)
    #14 0x7f9130c61f1f (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x49f1f)
    #15 0x7f9130c62241 in g_main_loop_run (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x4a241)
    #16 0x7f9132a03bf4 in gtk_main (/usr/lib/x86_64-linux-gnu/libgtk-3.so.0+0x1ebbf4)
    #17 0x7f913339d36b in dt_gui_gtk_run /home/lebedevri/darktable/src/gui/gtk.c:964
    #18 0x400cf3 in main /home/lebedevri/darktable/src/main.c:25
    #19 0x7f912ba49b44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b44)
    #20 0x400bd8 (/usr/local/bin/darktable+0x400bd8)

(cherry picked from commit 5cf182b)

Author: LebedevRI

src/control/control.c

@@ -281,6 +281,10 @@ void dt_ctl_set_display_profile()
     dt_print(DT_DEBUG_CONTROL, "[color profile] we got a new screen profile `%s' from the %s (size: %d)\n",
              *name ? name : "(unknown)", profile_source, buffer_size);
   }
+  else
+  {
+    g_free(buffer);
+  }
   pthread_rwlock_unlock(&darktable.control->xprofile_lock);
   if(profile_changed) dt_control_signal_raise(darktable.signals, DT_SIGNAL_CONTROL_PROFILE_CHANGED);
   g_free(profile_source);