fix warnings

lv_misc/lv_misc.mk

@@ -10,6 +10,7 @@ CSRCS += lv_color.c
 CSRCS += lv_txt.c
 CSRCS += lv_ufs.c
 CSRCS += lv_trigo.c
+CSRCS += lv_math.c
 
 DEPPATH += --dep-path lvgl/lv_misc
 VPATH += :lvgl/lv_misc

lv_misc/lv_task.c

@@ -130,7 +130,7 @@ LV_ATTRIBUTE_TASK_HANDLER void lv_task_handler(void)
  */
 lv_task_t* lv_task_create(void (*task) (void *), uint32_t period, lv_task_prio_t prio, void * param)
 {
-    lv_task_t* new_lv_task;
+    lv_task_t* new_lv_task = NULL;
     lv_task_t* tmp;
 
     /*Create task lists in order of priority from high to low*/