Bug 1293690

Description of problem:
When in replace command (s) isn't defined and address is defined by regexp, then sed use address regexp for replacing.

Version-Release number of selected component (if applicable):
sed (GNU sed) 4.2.2
sed-4.2.2-11.fc23.x86_64

How reproducible:
echo -e "foo\nbar" | sed '/o/s//X/'

Actual results:
fXo
bar

Expected results:
sed: -e expression #1, char 0: no previous regular expression

Additional info:
[jprokes@patejl Wallpapers ]$ echo -e "foo\nbar" | sed '/o/s//X/'
fXo
bar
[jprokes@patejl Wallpapers ]$ echo -e "foo\nbar" | sed '1s//X/'
sed: -e expression #1, char 0: no previous regular expression

When I compare these two commands, its behavior is inconsistent and possibly dangerous, in cases when sed is used inside larger bash script.