Fix all the defects identified by Clang Static Analyzer

Some fixes are dirty, but it is a start to enforce scan-build on
every commit.

Signed-off-by: pscott <scott.piriou@ledger.fr>

src_features/signMessageEIP712/ui_common_signMessage712.c

@@ -8,7 +8,6 @@ unsigned int io_seproxyhal_touch_signMessage712_v0_ok(__attribute__((unused))
     uint8_t privateKeyData[INT256_LENGTH];
     uint8_t hash[INT256_LENGTH];
     uint8_t signature[100];
-    uint8_t signatureLength;
     cx_ecfp_private_key_t privateKey;
     uint32_t tx = 0;
     io_seproxyhal_io_heartbeat();
@@ -43,14 +42,14 @@ unsigned int io_seproxyhal_touch_signMessage712_v0_ok(__attribute__((unused))
     explicit_bzero(privateKeyData, sizeof(privateKeyData));
     unsigned int info = 0;
     io_seproxyhal_io_heartbeat();
-    signatureLength = cx_ecdsa_sign(&privateKey,
-                                    CX_RND_RFC6979 | CX_LAST,
-                                    CX_SHA256,
-                                    hash,
-                                    sizeof(hash),
-                                    signature,
-                                    sizeof(signature),
-                                    &info);
+    cx_ecdsa_sign(&privateKey,
+                  CX_RND_RFC6979 | CX_LAST,
+                  CX_SHA256,
+                  hash,
+                  sizeof(hash),
+                  signature,
+                  sizeof(signature),
+                  &info);
     explicit_bzero(&privateKey, sizeof(privateKey));
     G_io_apdu_buffer[0] = 27;
     if (info & CX_ECCINFO_PARITY_ODD) {