Fix two minor compile-time issues (#1289)

src/lv_font/lv_font_fmt_txt.c

@@ -78,7 +78,7 @@ const uint8_t * lv_font_get_bitmap_fmt_txt(const lv_font_t * font, uint32_t unic
 {
     lv_font_fmt_txt_dsc_t * fdsc = (lv_font_fmt_txt_dsc_t *) font->dsc;
     uint32_t gid = get_glyph_dsc_id(font, unicode_letter);
-    if(!gid) return false;
+    if(!gid) return NULL;
 
     const lv_font_fmt_txt_glyph_dsc_t * gdsc = &fdsc->glyph_dsc[gid];
 

src/lv_objx/lv_ta.c

@@ -1707,7 +1707,6 @@ static void get_cursor_style(lv_obj_t * ta, lv_style_t * style_res)
         style_res->body.padding.top    = 0;
         style_res->body.padding.bottom = 0;
         style_res->line.width          = 1;
-        style_res->body.opa            = LV_OPA_COVER;
     }
 }