GL3: DG_dynarr.h errors shut down game now with Com_Error()

This means that allocations in dynamic arrays will never fail
(return NULL) but shut down the game instead.

So the github-advanced-security bot can shut up about null dereferences
(that were a very theoretical problem anyway, because malloc() is
 unlikely to return NULL in YQ2).

src/client/refresh/gl3/header/local.h

@@ -58,6 +58,9 @@
 
 #include "HandmadeMath.h"
 
+#define DG_DYNARR_ASSERT(cond, msg) \
+	((cond) ? (void)0 : Com_Error(ERR_FATAL, "DG_dynarr.h error: %s\n", msg))
+
 #if 0 // only use this for development ..
 #define STUB_ONCE(msg) do { \
 		static int show=1; \