Step 1:  code snippet provided does not directly show a CWE-476 (NULL Pointer Dereference) vulnerability in the line:
```
6 	char *sm_alternate = NULL, *error_strategy = NULL;
```
However, to reason about how a NULL pointer dereference vulnerability could occur, we need to consider the subsequent use of these pointers in the function `clone_submodule`. The vulnerability would typically manifest if these pointers are dereferenced without proper checks to ensure they are not NULL. Here’s a step-by-step analysis:

### Step 1: Initialization of Pointers
- The pointers `sm_alternate` and `error_strategy` are initialized to NULL.
- Initializing pointers to NULL is a common practice to ensure they are not pointing to arbitrary memory locations.

### Step 2: Potential Use of Pointers
- Since the actual usage of these pointers is not shown in the snippet, we must hypothesize based on common practices.
- These pointers might be intended to store addresses of strings or other data structures. If the function `clone_submodule` attempts to use these pointers (e.g., accessing data through them or passing them to other functions expecting valid addresses), it must first ensure they point to valid memory.

### Step 3: Hypothetical Vulnerable Behavior
- If `clone_submodule` or any function it calls tries to dereference `sm_alternate` or `error_strategy` without first checking if they are not NULL, it would lead to a NULL pointer dereference. For example:
  ```c
  if (strcmp(sm_alternate, "some_value") == 0) {
      // do something
  }
  ```
- In the above hypothetical code, if `sm_alternate` is still NULL when `strcmp` is called, it would cause a NULL pointer dereference because `strcmp` expects valid C-string pointers.

### Step 4: Ensuring Safety
- To prevent a NULL pointer dereference, the function should include checks before dereferencing these pointers:
  ```c
  if (sm_alternate != NULL && strcmp(sm_alternate, "some_value") == 0) {
      // do something
  }
  ```
- Additionally, the function might need to allocate memory or ensure that these pointers are assigned to valid addresses before any dereferencing occurs.

### Conclusion:
The vulnerability (CWE-476) would occur if there is an attempt to dereference `sm_alternate` or `error_strategy` without verifying that they have been assigned non-NULL values after their initialization. Proper checks should be implemented to ensure these pointers are valid before any operations that require dereferencing. The provided code snippet does not show the actual dereferencing, so the analysis assumes typical scenarios where such vulnerabilities might occur.
To address the CWE-476 NULL pointer dereference vulnerability potentially present in the code snippet provided, we need to ensure that any use of the pointers `sm_alternate` and `error_strategy` later in the code checks for NULL before dereferencing. Since the actual usage of these pointers isn't shown in the snippet, I will provide general strategies to safeguard against dereferencing NULL pointers.

### Patch 1: Add NULL Checks Before Usage
If `sm_alternate` and `error_strategy` are used later in the function, add checks before their usage:
```diff
- // Assuming somewhere in the code these pointers are dereferenced:
- some_function(sm_alternate, error_strategy);
+ if (sm_alternate != NULL && error_strategy != NULL) {
+     some_function(sm_alternate, error_strategy);
+ } else {
+     // Handle the error or return
+ }
```

### Patch 2: Initialize with Default Values
Instead of initializing to NULL, initialize these pointers with default valid values if applicable:
```diff
- char *sm_alternate = NULL, *error_strategy = NULL;
+ char *sm_alternate = default_alternate, *error_strategy = default_strategy;
```
*Note: `default_alternate` and `default_strategy` should be predefined valid strings.*

### Patch 3: Dynamic Allocation with Checks
Dynamically allocate memory for these pointers and check for successful allocation:
```diff
- char *sm_alternate = NULL, *error_strategy = NULL;
+ char *sm_alternate = malloc(DEFAULT_SIZE), *error_strategy = malloc(DEFAULT_SIZE);
+ if (!sm_alternate || !error_strategy) {
+     // Handle memory allocation failure
+     return -1;
+ }
```
*Note: `DEFAULT_SIZE` should be defined based on the expected size.*

### Patch 4: Function Parameter Validation
If these pointers are influenced by function parameters, validate those parameters before assignment:
```diff
+ if (clone_data == NULL || clone_data->alternate == NULL || clone_data->strategy == NULL) {
+     return -1;
+ }
  char *sm_alternate = clone_data->alternate, *error_strategy = clone_data->strategy;
```

### Patch 5: Safe Function Wrappers
Create or use safe wrapper functions that internally handle NULL pointers:
```diff
- some_function(sm_alternate, error_strategy);
+ safe_function(sm_alternate, error_strategy);
```
Where `safe_function` is defined as:
```c
void safe_function(char *alt, char *strat) {
    if (alt == NULL || strat == NULL) {
        // Handle NULL case
        return;
    }
    // Proceed with actual function logic
}
```

Each of these patches provides a strategy to mitigate potential NULL pointer dereferences based on different assumptions about how `sm_alternate` and `error_strategy` are used in the broader context of the code. The best choice depends on the specific use case and existing code structure.