Prevent assertions outside sections from crashing

include/link/patch.h

@@ -22,6 +22,11 @@ struct Assertion {
 	// enum AssertionType type; The `patch`'s field is instead re-used
 	struct Section *section;
 	char *message;
+	/*
+	 * This would be redundant with `.section->fileSymbols`... but
+	 * `section` is sometimes NULL!
+	 */
+	struct Symbol ** fileSymbols;
 
 	struct Assertion *next;
 };