jcov, jtime, jtrace: fix not removing callback

Author: dbohdan

examples/jcov

@@ -25,7 +25,7 @@ xtrace xcov
 # Catch exit but not error
 set rc [catch -noerror -exit {source $argv0} msg opts]
 
-xtrace
+xtrace {}
 
 proc show-coverage {filename} {
 	set info $::coverage($filename)

examples/jtime

@@ -31,7 +31,7 @@ xtrace jtime::xtrace
 # Catch exit but not error
 set rc [catch -noerror -exit {source $argv0} msg opts]
 
-xtrace
+xtrace {}
 
 set info $jtime::fileinfo($argv0)
 

examples/jtrace

@@ -20,4 +20,4 @@ xtrace jtime::xtrace
 # Catch exit but not error
 set rc [catch -noerror -exit {source $argv0} msg opts]
 
-xtrace
+xtrace {}