GATT: Fix GATT error response for execute write

Usecaes:
Execute GATT/SR/GAW/BI-09C

Expected Result:
Test case passes

Observed Result:
Unable to pass the test cases

Root Cause:
Incorrect error response sent by DUT if there is no pending write request

Fix:
Send GATT_INVALID_OFFSET error when no pending write request

Test: GATT/SR/GAW/BI-09C passes

Bug: 80168519
Change-Id: I74e723ab0e39ce04e21f929a16dffcd996d1d23e