Fix code generation for LL1OptionalBlock bypass alternative

See #1545

tool/resources/org/antlr/v4/tool/templates/codegen/CSharp/CSharp.stg

@@ -566,7 +566,7 @@ switch (TokenStream.LA(1)) {
 	<alt>
 	break;}; separator="\n">
 default:
-	<error>
+	break;
 }
 >>
 

tool/resources/org/antlr/v4/tool/templates/codegen/Cpp/Cpp.stg

@@ -644,7 +644,7 @@ switch (_input->LA(1)) {
 \}
 }; separator="\n">
 default:
-  <error>
+  break;
 }
 >>
 

tool/resources/org/antlr/v4/tool/templates/codegen/Go/Go.stg

@@ -563,9 +563,6 @@ switch p.GetTokenStream().LA(1) {
 
 <endif>
 default:
-	<if(error)>
-	<error>
-	<endif>
 }
 >>
 

tool/resources/org/antlr/v4/tool/templates/codegen/Java/Java.stg

@@ -489,7 +489,7 @@ switch (_input.LA(1)) {
 	<alt>
 	break;}; separator="\n">
 default:
-	<error>
+	break;
 }
 >>
 

tool/resources/org/antlr/v4/tool/templates/codegen/JavaScript/JavaScript.stg

@@ -360,7 +360,7 @@ switch (this._input.LA(1)) {
 	<alt>
 	break;}; separator="\n">
 default:
-	<error>
+	break;
 }
 >>
 

tool/resources/org/antlr/v4/tool/templates/codegen/Python2/Python2.stg

@@ -334,7 +334,7 @@ token = self._input.LA(1)
     <alt>
     pass}; separator="\nel">
 else:
-    <error>
+    pass
 >>
 
 LL1OptionalBlockSingleAlt(choice, expr, alts, preamble, error, followExpr) ::= <<

tool/resources/org/antlr/v4/tool/templates/codegen/Python3/Python3.stg

@@ -342,7 +342,7 @@ token = self._input.LA(1)
     <alt>
     pass}; separator="\nel">
 else:
-    <error>
+    pass
 >>
 
 LL1OptionalBlockSingleAlt(choice, expr, alts, preamble, error, followExpr) ::= <<

tool/resources/org/antlr/v4/tool/templates/codegen/Swift/Swift.stg

@@ -510,7 +510,7 @@ switch (<parser.name>.Tokens(rawValue: try _input.LA(1))!) {
  	<alt>
 	break}; separator="\n">
 default:
-	<error>
+	break
 }
 >>