Test: Fix crash when loading invalid file

CHANGES

@@ -45,6 +45,7 @@ Bugfixes:
  - GBA Video: Don't update background scanline params in mode 0 (fixes mgba.io/i/377)
  - Qt: Ensure CLI backend is attached when submitting commands (fixes mgba.io/i/662)
  - Core: Fix crash with rewind if savestates shrink
+ - Test: Fix crash when loading invalid file
 Misc:
  - SDL: Remove scancode key input
  - GBA Video: Clean up unused timers

src/platform/test/fuzz-main.c

@@ -68,6 +68,9 @@ int main(int argc, char** argv) {
 		return 0;
 	}
 	struct mCore* core = mCoreFind(args.fname);
+	if (!core) {
+		return 1;
+	}
 	core->init(core);
 	mCoreInitConfig(core, "fuzz");
 	applyArguments(&args, NULL, &core->config);