CryptEc.c CodeQL Fix (#492)

## Description

Free calls could have been called with NULL arguments.

- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [x] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

Tested on Q35

## Integration Instructions

N/A

---------

Co-authored-by: Taylor Beebe <t@taylorbeebe.com>

CryptoPkg/Library/BaseCryptLib/Pk/CryptEc.c

@@ -585,6 +585,11 @@ EcGetPubKey (
     return FALSE;
   }
 
+  // MU_CHANGE [BEGIN] - CodeQL change
+  BnX = NULL;
+  BnY = NULL;
+  // MU_CHANGE [END] - CodeQL change
+
   EcKey    = (EC_KEY *)EcContext;
   Group    = EC_KEY_get0_group (EcKey);
   HalfSize = (EC_GROUP_get_degree (Group) + 7) / 8;
@@ -628,8 +633,16 @@ EcGetPubKey (
   RetVal = TRUE;
 
 fail:
-  BN_free (BnX);
-  BN_free (BnY);
+  // MU_CHANGE [BEGIN] - CodeQL change
+  if (BnX != NULL) {
+    BN_free (BnX);
+  }
+
+  if (BnY != NULL) {
+    BN_free (BnY);
+  }
+
+  // MU_CHANGE [END] - CodeQL change
   return RetVal;
 }