Fix an infinite loop caused by a corrupt database in fts3. Also an undefined

left-shift in fts5.

FossilOrigin-Name: 55c5d72af9510e2f27c33544d804a58d4282b0efb384ead38484129ce91b574f

ext/fts5/fts5_buffer.c

@@ -52,7 +52,7 @@ void sqlite3Fts5Put32(u8 *aBuf, int iVal){
 }
 
 int sqlite3Fts5Get32(const u8 *aBuf){
-  return (aBuf[0] << 24) + (aBuf[1] << 16) + (aBuf[2] << 8) + aBuf[3];
+  return (int)((((u32)aBuf[0])<<24) + (aBuf[1]<<16) + (aBuf[2]<<8) + aBuf[3]);
 }
 
 /*

ext/fts5/test/fts5corrupt3.test

@@ -4639,6 +4639,18 @@ do_catchsql_test 37.1 {
   SELECT * FROM t3;
 } {1 {database disk image is malformed}}
 
+#-------------------------------------------------------------------------
+reset_db 
+do_execsql_test 37.0 {
+  CREATE VIRTUAL TABLE t1 USING fts5(b, c);
+  INSERT INTO t1 VALUES('a', 'b');
+  SELECT quote(block) FROM t1_data WHERE rowid=10;
+} {X'000000000101010001010101'}
+
+do_execsql_test 37.1 {
+  UPDATE t1_data SET block = X'FFFFFFFF0101010001010101' WHERE rowid = 10;
+  SELECT rowid FROM t1('a');
+} {1}