patch 9.0.0057: has('patch-xxx') returns true

Problem:    has('patch-xxx') returns true.
Solution:   Check for digit. (closes #10751)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index f51aade..580f5d1 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -6473,7 +6473,7 @@
 			     || (minor == VIM_VERSION_MINOR
 				 && has_patch(atoi((char *)name + 10))))));
 	    }
-	    else
+	    else if (isdigit(name[5]))
 		n = has_patch(atoi((char *)name + 5));
 	}
 	else if (STRICMP(name, "vim_starting") == 0)