Log: ensure fmt

Utilities/cfmt.h

@@ -15,6 +15,8 @@ C-style format parser. Appends formatted string to `out`, returns number of char
 template<typename Dst, typename Char, typename Src>
 usz cfmt_append(Dst& out, const Char* fmt, Src&& src)
 {
+	ensure(fmt);
+
 	const usz start_pos = out.size();
 
 	struct cfmt_context

rpcs3/Emu/System.cpp

@@ -1989,6 +1989,8 @@ s32 error_code::error_report(s32 result, const char* fmt, const fmt_type_info* s
 		}
 	}
 
+	ensure(fmt);
+
 	logs::channel* channel = &sys_log;
 	const char* func = "Unknown function";