Unexpected StringIndexOutOfBoundsException with empty string

[YuanchengJiang]

Describe the bug

psycopg.OperationalError: consuming input failed: server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.

java.lang.StringIndexOutOfBoundsException: String index out of range: 0
	at java.lang.StringLatin1.charAt(StringLatin1.java:48)
	at java.lang.String.charAt(String.java:1513)
	at io.questdb.griffin.ExpressionParser.parseExpr(ExpressionParser.java:286)
	at io.questdb.griffin.SqlParser.expr(SqlParser.java:2190)
	at io.questdb.griffin.SqlParser.parseFromClause(SqlParser.java:1138)
	at io.questdb.griffin.SqlParser.parseDml0(SqlParser.java:921)
	at io.questdb.griffin.SqlParser.parseDml(SqlParser.java:816)
	at io.questdb.griffin.SqlParser.parseSelect(SqlParser.java:1550)
	at io.questdb.griffin.SqlParser.parse(SqlParser.java:2219)
	at io.questdb.griffin.SqlCompiler.compileExecutionModel(SqlCompiler.java:1158)
	at io.questdb.griffin.SqlCompiler.compileUsingModel(SqlCompiler.java:1244)
	at io.questdb.griffin.SqlCompiler.compileInner(SqlCompiler.java:1213)
	at io.questdb.griffin.SqlCompiler.compileBatch(SqlCompiler.java:261)
	at io.questdb.cutlass.pgwire.PGConnectionContext.processQuery(PGConnectionContext.java:2414)
	at io.questdb.cutlass.pgwire.PGConnectionContext.parse(PGConnectionContext.java:1691)
	at io.questdb.cutlass.pgwire.PGConnectionContext.handleClientOperation(PGConnectionContext.java:421)
	at io.questdb.cutlass.pgwire.PGJobContext.handleClientOperation(PGJobContext.java:89)
	at io.questdb.cutlass.pgwire.PGWireServer$1.lambda$$0(PGWireServer.java:91)
	at io.questdb.network.AbstractIODispatcher.processIOQueue(AbstractIODispatcher.java:189)
	at io.questdb.cutlass.pgwire.PGWireServer$1.run(PGWireServer.java:128)
	at io.questdb.mp.Worker.run(Worker.java:118)

To reproduce

Run
select 1 from telemetry where ("")

Note:
It does not stably reproduce the bug but should be reproducible after several tries.

Another case it gave DatabaseError: unbalanced ( which is also weired

Expected Behavior

No response

Environment

- **QuestDB version**: 7.1.3
- **OS**: ubuntu 20.04

Additional context

No response