Provide graceful fall back if theme is not available.

This is a bit of a hack since it hardwires math4 theme as the default theme that is always available.  A future iteration should make this defaultDefaultTheme configurable in defaults.config. (We should also clean up the variable names. :-) )

lib/WeBWorK/ContentGenerator.pm

@@ -492,7 +492,20 @@ sub content {
 	# this means that the {stylesheet} option in defaults.config is never used
 	my $template = $self->can("templateName") ? $self->templateName : $ce->{defaultThemeTemplate};
 	my $templateFile = "$themesDir/$theme/$template.template";
-
+	unless (-r $templateFile) {  #hack to prevent disaster when missing theme directory
+	   if (-r "$themesDir/math4/$template.template") {
+	   		$templateFile = "$themesDir/math4/$template.template";
+	   		warn "Theme $theme is not one of the available themes. ".
+	   		"Please check the theme configuration ".
+	   		"in the files localOverrides.conf, course.conf and ".
+	   		"simple.conf and on the course configuration page.\n"
+	   	} else {
+	   		die "Neither the theme $theme nor the defaultTheme math4 are available.  ".  
+	   		"Please notify your site administrator that the structure of the ".
+	   		"themes directory needs attention.";
+
+	   	}
+	}
 	template($templateFile, $self);
 }
 
@@ -1020,8 +1033,8 @@ sub footer(){
 	my $self = shift;
 	my $r = $self->r;
 	my $ce = $r->ce;
-	my $ww_version = $ce->{WW_VERSION}||"unknown -- set ww version in defaults.config";
-	my $pg_version = $ce->{PG_VERSION}||"unknown -- set pg version in defaults.config";
+	my $ww_version = $ce->{WW_VERSION}||"unknown -- set ww version VERSION";
+	my $pg_version = $ce->{PG_VERSION}||"unknown -- set pg version PG_VERSION link to ../pg/VERSION";
 	my $theme = $ce->{defaultTheme}||"unknown -- set defaultTheme in localOverides.conf";
 	my $copyright_years = $ce->{WW_COPYRIGHT_YEARS}||"1996-2011";
 	print CGI::div({-id=>"last-modified"}, $r->maketext("Page generated at [_1]", timestamp($self)));