Added guard condition to seek

Fixed guard condition in filesize to exit properly

userprog/syscall_filesize.c

@@ -13,6 +13,7 @@ void syscall_filesize(struct intr_frame *f) {
 	struct file *file = get_associated_file_pointer(file_descriptor);
 	if (file == NULL) { // Checking if file is empty or non-existent
 		f->eax -1; // Returning failure state
+		return;
 	}
 	// Using the file_length function in file.h to get the length and store it
 	int size = file_length(file); 

userprog/syscall_seek.c

@@ -17,6 +17,9 @@ void syscall_seek(struct intr_frame *f) {
 	// pop off second int argument from interrupt frame
 	unsigned file_pos = *((unsigned*)((int*)f->esp + 2));
 	struct file *file = get_associated_file_pointer(file_descriptor);
+	if (file == NULL) { // Checking if file is empty or non-existent
+		return;
+	}
 	// Seek through the file
 	file_seek(file, file_pos);
 }