rARCb996b4799b02

phutil_nonempty_scalar(): don't throw when receiving a boolean scalar

Summary:
Note that booleans are scalars. Full stop.

| is_scalar($v) | Result |
|------------------|--------|
| `"foo"` | true |
| `""` | true |
| `null` | true |
| `0` | true |
| `0.5` | true |
| `true` | true |
| `false` | true |
| `new stdclass()` | false |
| `array()` | false |

Note that phutil_nonempty_scalar() was designed just to…