patch 9.0.0811: error if :echowin is preceded by a command modifier

Problem:    Error if :echowin is preceded by a command modifier.
Solution:   Do not give an error for range when there is a modifier.
            (closes #11414)
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 73bfa6c..fb66a78 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -2712,8 +2712,9 @@
 	;
     if (!isdigit(*p))
     {
-	// the command must be following
-	if (p < eap->cmd)
+	// The command or modifiers must be following.  Assume a lower case
+	// character means there is a modifier.
+	if (p < eap->cmd && !vim_islower(*p))
 	{
 	    emsg(_(e_invalid_range));
 	    return -1;