[maxwell] Fix Flow::Block comp error (#3882)

Signed-off-by: crueter <crueter@eden-emu.dev>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3882
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/shader_recompiler/frontend/maxwell/structured_control_flow.cpp

@@ -979,7 +979,7 @@ private:
     Environment& env;
     IR::AbstractSyntaxList& syntax_list;
     bool uses_demote_to_helper{};
-    const Flow::Block dummy_flow_block;
+    const Flow::Block dummy_flow_block{};
 };
 } // Anonymous namespace