[bash] Hide the stderr of __svn_ps1 (if subversion is not installed)

bash/bashrc

@@ -114,13 +114,16 @@ HISTTIMEFORMAT="[%d/%m/%Y %H:%M:%S] "
 
 ## display the current subversion revision (to be used later in the prompt)
 __svn_ps1() {
-  local svnversion
-  svnversion=$(svnversion | sed -e "s/[:M]//g")
-  # Continue if $svnversion is numerical
-  if let $svnversion 2>/dev/null
-  then
-    printf " (svn:%s)" "$(svnversion)"
-  fi
+  (
+    local svnversion
+    svnversion=$(svnversion | sed -e "s/[:M]//g")
+    # Continue if $svnversion is numerical
+    let $svnversion
+    if [[ "$?" -eq "0" ]]
+    then
+      printf " (svn:%s)" "$(svnversion)"
+    fi
+  ) 2>/dev/null
 }
 
 # render __git_ps1 even better so as to show activity in a git repository