Add check if variable exists

src/main.c

@@ -79,8 +79,11 @@ int parse_command(char **command, int status) {
 					char status_string[256]; // FIXME
 					sprintf(status_string, "%d", status);
 					command[i] = status_string;
-				} else
+				} else {
 					command[i] = getenv(command[i]);
+					if (command[i] == NULL) 
+						command[i] = "";
+				}
 			}
 		}
 	}