patch 8.2.4214: illegal memory access with large 'tabstop' in Ex mode

Problem:    Illegal memory access with large 'tabstop' in Ex mode.
Solution:   Allocate enough memory.
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 5dc43d8..097b97e 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -1513,7 +1513,7 @@
     ccline.cmdindent = (firstc > 0 ? indent : 0);
 
     // alloc initial ccline.cmdbuff
-    alloc_cmdbuff(exmode_active ? 250 : indent + 1);
+    alloc_cmdbuff(indent + 50);
     if (ccline.cmdbuff == NULL)
 	return FAIL;
     ccline.cmdlen = ccline.cmdpos = 0;