Kill off some silly casting in the FifoPlayer.

Also makes more sense conceptually, since it's not like we'll ever have negative frames.

Source/Core/Core/FifoPlayer/FifoDataFile.h

@@ -64,8 +64,8 @@ public:
 	u32 *GetXFRegs() { return m_XFRegs; }
 
 	void AddFrame(const FifoFrameInfo &frameInfo);
-	const FifoFrameInfo &GetFrame(int frame) const { return m_Frames[frame]; }
-	int GetFrameCount() { return (int)m_Frames.size(); }
+	const FifoFrameInfo &GetFrame(size_t frame) const { return m_Frames[frame]; }
+	size_t GetFrameCount() { return m_Frames.size(); }
 
 	bool Save(const char *filename);