fix: nvm strcmp should crash on NULL, color cmd is now protected though

src/shell/commands/color_cmd.c

@@ -13,12 +13,16 @@ void color_cmd(char *arg)
 	    "DARK_GREY", "LIGHT_BLUE",    "LIGHT_GREEN",  "LIGHT_CYAN",
 	    "LIGHT_RED", "LIGHT_MAGENTA", "LIGHT_YELLOW", "WHITE",
 	};
+
+	if (!arg)
+		goto invalid;
 	for (size_t i = 0; i < ARRAY_SIZE(colors); i++) {
 		if (strcmp(colors[i], arg) == 0) {
 			terminal_change_default_fg_color(i);
 			return;
 		}
 	}
+invalid:
 	tmp_color = terminal_get_default_color();
 	kprintf(KERN_WARNING "Invalid argument\n");
 	kprintf("Available colors: ");