Support for extra card fields in stylesheets;

Fixed some bugs:
 - Missing choice images can crash mse.
 - The wrong style is used for making preview choice images on style panel.
FOR_EACH(x, *y.z) should now work without parentheses on linux as well.

git-svn-id: svn://svn.code.sf.net/p/magicseteditor/code/trunk@389 0fc631ac-6414-0410-93d0-97cfa31319b6

src/util/error.cpp

@@ -55,10 +55,12 @@ vector<String> previous_errors;
 String pending_errors;
 String pending_warnings;
 DECLARE_TYPEOF_COLLECTION(String);
+wxCriticalSection crit_error_handling;
 
 void handle_error(const String& e, bool allow_duplicate = true, bool now = true) {
+	// Thread safety
+	wxCriticalSectionLocker lock(crit_error_handling);
 	// Check duplicates
-	// TODO: thread safety
 	if (!allow_duplicate) {
 		FOR_EACH(pe, previous_errors) {
 			if (e == pe) return;