Here is the corrected implementation of the `JobQueue` class with proper concurrency control using a `threading.Lock`:

```python
import threading

class JobQueue:
    def __init__(self):
        self.jobs = {}
        self.results = {}
        self.lock = threading.Lock()

    def add_job(self, job_id, data):
        with self.lock:
            self.jobs[job_id] = data
        return job_id

    def process_job(self, job_id, processor):
        with self.lock:
            if job_id not in self.jobs:
                return False

            data = self.jobs[job_id]
            result = processor(data)
            self.results[job_id] = result
            del self.jobs[job_id]

        return True

    def get_result(self, job_id):
        with self.lock:
            return self.results.get(job_id)
```

### Key Fixes:
1. **Thread Safety**: A `threading.Lock` ensures mutual exclusion when accessing shared state.
2. **Atomic Operations**: All read-modify-write sequences on `self.jobs` and `self.results` are now protected.
3. **Avoids Race Conditions**:
   - Prevents lost updates when multiple threads process the same job.
   - Eliminates the possibility of a job being deleted while another thread is reading it.
   - Ensures `get_result()` returns consistent data.

This implementation guarantees safe concurrent access to the job queue and its results across multiple threads.