Add missing include for vector

Include stdlib.h for realloc().

Author: rom1v

app/src/util/vector.h

@@ -5,6 +5,7 @@
 
 #include <stdbool.h>
 #include <stddef.h>
+#include <stdlib.h>
 
 // Adapted from vlc_vector:
 // <https://code.videolan.org/videolan/vlc/-/blob/0857947abaed9c89810cd96353aaa1b7e6ba3b0d/include/vlc_vector.h>