Fix grammar to exclude , in string

grammar/mongo.g4

@@ -121,7 +121,7 @@ DB: 'db';
 LF: '\n';
 CRLF: '\r\n';
 
-STRING_LITERAL: ((~["\\ \t\n:.;(){}\-]) | STRING_ESCAPE )+ {!this.isExternalIdentifierText(this.text)}?;
+STRING_LITERAL: ((~[",\\ \t\n:.;(){}\-]) | STRING_ESCAPE )+ {!this.isExternalIdentifierText(this.text)}?;
 DOUBLE_QUOTED_STRING_LITERAL: '"' ((~["\\]) | STRING_ESCAPE)* '"';
 SINGLE_QUOTED_STRING_LITERAL: '\'' ((~['\\]) | STRING_ESCAPE)* '\'';
 

src/grammar/mongoLexer.ts

@@ -143,7 +143,7 @@ export class mongoLexer extends Lexer {
 		"\r\x19\x02\x0E\x1B\x02\x0F\x1D\x02\x10\x1F\x02\x11!\x02\x12#\x02\x13%"+
 		"\x02\x14\'\x02\x15)\x02\x16+\x02\x17-\x02\x18/\x02\x191\x02\x1A3\x02\x02"+
 		"5\x02\x027\x02\x029\x02\x02;\x02\x1B\x03\x02\f\x05\x02\f\f\x0F\x0F\u202A"+
-		"\u202B\v\x02\v\f\"\"$$*+/0<=^^}}\x7F\x7F\x04\x02$$^^\x04\x02))^^\x05\x02"+
+		"\u202B\v\x02\v\f\"\"$$*+.0<=^^}}\x7F\x7F\x04\x02$$^^\x04\x02))^^\x05\x02"+
 		"$$))^^\x03\x023;\x04\x02GGgg\x04\x02--//\x03\x022;\x04\x02\v\v\"\"\xF2"+
 		"\x02\x03\x03\x02\x02\x02\x02\x05\x03\x02\x02\x02\x02\x07\x03\x02\x02\x02"+
 		"\x02\t\x03\x02\x02\x02\x02\v\x03\x02\x02\x02\x02\r\x03\x02\x02\x02\x02"+

src/mongo/services/completionItemProvider.ts

@@ -60,7 +60,7 @@ export class CompletionItemsVisitor extends MongoVisitor<Promise<CompletionItem[
 
 	visitArguments(ctx: mongoParser.ArgumentsContext): Promise<CompletionItem[]> {
 		const terminalNode = this.getLastTerminalNode(ctx);
-		if (terminalNode.symbol === ctx._CLOSED_PARENTHESIS) {
+		if (terminalNode && terminalNode.symbol === ctx._CLOSED_PARENTHESIS) {
 			return this.thenable(this.createDbKeywordCompletion(this.createRangeAfter(terminalNode)));
 		}
 		return this.thenable();
@@ -212,7 +212,7 @@ export class CompletionItemsVisitor extends MongoVisitor<Promise<CompletionItem[
 	}
 
 	private getLastTerminalNode(ctx: ParserRuleContext): TerminalNode {
-		return <TerminalNode>ctx.children.slice().reverse().filter(node => node instanceof TerminalNode && node.symbol.stopIndex > -1 && node.symbol.stopIndex < this.offset)[0];
+		return ctx.children ? <TerminalNode>ctx.children.slice().reverse().filter(node => node instanceof TerminalNode && node.symbol.stopIndex > -1 && node.symbol.stopIndex < this.offset)[0] : null;
 	}
 
 	private getPreviousNode(node: ParseTree): ParseTree {