Fix 2 error (#71)

* Update datafile.c

lcc: "/root/dev/dethrace/src/BRSRC13/CORE/FW/datafile.c", строка 409: ошибка:
         переменная "n" может быть использована неинициализированной
         [-Werror=maybe-uninitialized]

* Update common.c
"scancode unsigned" can't be below zero.

src/BRSRC13/CORE/FW/datafile.c

@@ -404,6 +404,7 @@ br_uint_32 DfStructReadBinary(br_datafile* df, br_file_struct* str, void* base)
         case 31:
             n = 4;
             break;
+        default: n = 0;
         }
 
         for (i = 0; i < n; i++) {

src/harness/sdl/common.c

@@ -128,7 +128,7 @@ void SDLPlatform_PollEvents() {
 
         case SDL_KEYDOWN:
         case SDL_KEYUP:
-            if (event.key.keysym.scancode < 0 || event.key.keysym.scancode > 122) {
+            if (event.key.keysym.scancode > 122) {
                 LOG_WARN("unexpected scan code %d", event.key.keysym.scancode);
                 return;
             }