falcon: conversion warning

crypto_sign/falcon-1024/clean/codec.c

@@ -444,7 +444,9 @@ PQCLEAN_FALCON1024_CLEAN_comp_decode(
             }
         }
         x[u] = (int16_t) m;
-        if (s) x[u] = -x[u];
+        if (s) {
+          x[u] = (int16_t) -x[u];
+        }
     }
     return v;
 }

crypto_sign/falcon-512/clean/codec.c

@@ -444,7 +444,9 @@ PQCLEAN_FALCON512_CLEAN_comp_decode(
             }
         }
         x[u] = (int16_t) m;
-        if (s) x[u] = -x[u];
+        if (s) {
+          x[u] = (int16_t) -x[u];
+        }
     }
     return v;
 }