The uncached/cached error message says not to do this:
[[If? &subject=`[[+modx.user.id]]` &operator=`EQ` &operand=`0` &then=`[[$call_Login]]` &else=`[[!$qui-est-la]]` ]]
The exclamation point on the inner chunk tag will delay the processing of that tag, so the intended content won't be available when the If snippet runs. What the If snippet gets as an argument will likely be the tag itself which can blow up during error processing.
So, three options to stop that error:
1) No exclamation points -- should be fine unless the chunk is often being altered dynamically in code.
[[If? &subject=`[[+modx.user.id]]` &operator=`EQ` &operand=`0` &then=`[[$call_Login]]` &else=`[[$qui-est-la]]` ]]
2) One Exclamation point -- Results will be up-to-date if chunk is up-to-date.
[[!If? &subject=`[[+modx.user.id]]` &operator=`EQ` &operand=`0` &then=`[[$call_Login]]` &else=`[[$qui-est-la]]` ]]
2) Two exclamation points -- slows page loads but could be necessary on rare occasions:
[[!If? &subject=`[[+modx.user.id]]` &operator=`EQ` &operand=`0` &then=`[[$call_Login]]` &else=`[[!$qui-est-la]]` ]]