git-gui: Ensure all spellchecker 'class' variables are initialized

If we somehow managed to get our spellchecker instance created but
aspell wasn't startable we may not finish _connect and thus may
find one or more of our fields was not initialized in the instance.

If we have an instance but no version, there is no reason to show
a version to the user in our about dialog.  We effectively have no
spellchecker available.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

lib/about.tcl

@@ -41,7 +41,8 @@ proc do_about {} {
 		append v "Tcl version $tcl_patchLevel"
 		append v ", Tk version $tk_patchLevel"
 	}
-	if {[info exists ui_comm_spell]} {
+	if {[info exists ui_comm_spell]
+		&& [$ui_comm_spell version] ne {}} {
 		append v "\n"
 		append v [$ui_comm_spell version]
 	}

lib/spellcheck.tcl

@@ -3,15 +3,15 @@
 
 class spellcheck {
 
-field s_fd     {} ; # pipe to aspell
+field s_fd      {} ; # pipe to aspell
-field s_version   ; # aspell version string
+field s_version {} ; # aspell version string
-field s_lang      ; # current language code
+field s_lang    {} ; # current language code
 
 field w_text      ; # text widget we are spelling
 field w_menu      ; # context menu for the widget
 field s_menuidx 0 ; # last index of insertion into $w_menu
 
-field s_i              ; # timer registration for _run callbacks
+field s_i           {} ; # timer registration for _run callbacks
 field s_clear        0 ; # did we erase mispelled tags yet?
 field s_seen    [list] ; # lines last seen from $w_text in _run
 field s_checked [list] ; # lines already checked
@@ -21,6 +21,7 @@ field s_suggest        ; # array, list of suggestions, keyed by misspelling
 constructor init {pipe_fd ui_text ui_menu} {
 	set w_text $ui_text
 	set w_menu $ui_menu
+	array unset s_suggest
 
 	_connect $this $pipe_fd
 	return $this
@@ -88,7 +89,10 @@ method lang {{n {}}} {
 }
 
 method version {} {
-	return "$s_version, $s_lang"
+	if {$s_version ne {}} {
+		return "$s_version, $s_lang"
+	}
+	return {}
 }
 
 method stop {} {