supply a default constructor

stepmania/src/RageUtil.cpp

@@ -667,17 +667,23 @@ void Regex::Compile()
     ASSERT(backrefs+1 < 128);
 }
 
+void Regex::Set(const CString &str)
+{
+	Release();
+    pattern=str;
+	Compile();
+}
+
 void Regex::Release()
 {
     delete (regex_t *)reg;
 	reg = NULL;
 }
 
-Regex::Regex(const CString &pattern_)
+Regex::Regex(const CString &str)
 {
 	reg = NULL;
-    pattern=pattern_;
-	Compile();
+	Set(str);
 }
 
 Regex::Regex(const Regex &rhs)

stepmania/src/RageUtil.h

@@ -207,9 +207,10 @@ class Regex {
     void Compile();
     void Release();
 public:
-	Regex(const CString &pat);
+	Regex(const CString &pat = "");
 	Regex(const Regex &rhs);
 	~Regex();
+	void Set(const CString &str);
 	bool Compare(const CString &str);
 	bool Compare(const CString &str, vector<CString> &matches);
 };