patch 9.1.1242: Crash when evaluating variable name

Problem:  Crash when evaluating variable name (after v9.1.0870)
Solution: calculate the strlen() directly instead of pointer
          arithmetics, fix missing assignment to lp->ll_name_end in
          get_lval() (zeertzjq)

closes: #16972
fixes: vim-airline/vim-airline#2710
related: #16066

Co-authored-by: zeertzjq <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: chrisbra

src/eval.c

@@ -2163,6 +2163,8 @@ get_lval(
 	    }
 	}
 	lp->ll_name = lp->ll_exp_name;
+	if (lp->ll_name != NULL)
+	    lp->ll_name_end = lp->ll_name + STRLEN(lp->ll_name);
     }
     else
     {
@@ -2373,7 +2375,7 @@ set_var_lval(
 
 	    // handle +=, -=, *=, /=, %= and .=
 	    di = NULL;
-	    if (eval_variable(lp->ll_name, (int)(lp->ll_name_end - lp->ll_name),
+	    if (eval_variable(lp->ll_name, (int)STRLEN(lp->ll_name),
 				 lp->ll_sid, &tv, &di, EVAL_VAR_VERBOSE) == OK)
 	    {
 		if (di != NULL && check_typval_is_value(&di->di_tv) == FAIL)

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1242,
 /**/
     1241,
 /**/