patch 8.1.0074: crash when running quickfix tests

Problem:    Crash when running quickfix tests.
Solution:   Do not alloc a new location list when checking for the reference
            to be still valid.

src/quickfix.c

@@ -6350,7 +6350,7 @@ ex_cexpr(exarg_T *eap)
 						curbuf->b_fname, TRUE, curbuf);
 	    if (res > 0 && (eap->cmdidx == CMD_cexpr
 						   || eap->cmdidx == CMD_lexpr)
-		    && qi == ll_get_or_alloc_list(curwin))
+		    && qi == GET_LOC_LIST(curwin))
 		// Jump to the first error if autocmds didn't free the list.
 		qf_jump(qi, 0, 0, eap->forceit);
 	}