Cartridge: fixed crash on broken rom files if we can fix it

This hasn't happened before, but the mbc1 test rom in gbmicrotest is not correct. We can gracefully fix it.

mizu-core/src/cartridge.rs

@@ -281,10 +281,27 @@ impl Cartridge {
             return Err(CartridgeError::InvalidRomSizeIndex(data[0x148]));
         }
 
-        let rom_size = 0x8000 << num_rom_banks;
+        let mut rom_size = 0x8000 << num_rom_banks;
 
         if rom_size != data.len() {
-            return Err(CartridgeError::InvalidRomSize(rom_size));
+            // try to fix it, sometimes the rom will have `0` as the num_rom_banks
+            let mut fixed = false;
+            if rom_size < data.len() && data.len() % rom_size == 0 {
+                let div = data.len() / rom_size;
+                if div.is_power_of_two() && div.ilog2() < 8 {
+                    println!(
+                        "WARN: invalid cartridge header. Using rom size {:X} instead of {:X}",
+                        data.len(),
+                        rom_size,
+                    );
+                    rom_size = data.len();
+                    fixed = true;
+                }
+            }
+
+            if !fixed {
+                return Err(CartridgeError::InvalidRomSize(rom_size));
+            }
         }
 
         let ram_size = match data[0x149] {

mizu-core/src/tests/gbmicrotest.rs

@@ -278,7 +278,7 @@ gbmicrotest_tests!(
     // lyc2_int_halt_a,
     lyc2_int_halt_b,
     mbc1_ram_banks,
-    // mbc1_rom_banks,
+    mbc1_rom_banks,
     // minimal,
     // mode2_stat_int_to_oam_unlock,
     // oam_int_halt_a,