- handle JIT errors in a more user-friendly fashion than aborting.

* use I_Error instead of I_FatalError to abort. I_FatalError is only for things that are not recoverable and should not be handled outside of error cleanup and rethrowing.
* only catch CRecoverableError in JitCompile. Everything else should fall through to the outermost catch block.
* Do not I_FatalError out after handling the exception locally. Just print an error and return null, indicating failure.

src/scripting/vm/jit_move.cpp

@@ -174,7 +174,7 @@ void JitCompiler::EmitCAST()
 		call->setArg(1, regD[B]);
 		break;
 	default:
-		I_FatalError("Unknown OP_CAST type\n");
+		I_Error("Unknown OP_CAST type\n");
 	}
 }