[fix] line tool bug with tool locked (#1841)

This PR fixes a bug where tool lock would cause the line tool to not
work properly.

### Change Type

- [x] `patch` — Bug fix

### Test Plan

1. Turn on tool lock.
2. Draw two line shapes

- [x] Unit Tests

packages/tldraw/src/lib/shapes/line/LineShapeTool.test.ts

@@ -209,3 +209,20 @@ describe('When extending the line with the shift-key in tool-lock mode', () => {
 		expect(handles.length).toBe(3)
 	})
 })
+
+describe('tool lock bug', () => {
+	it('works as expected when tool lock is on but shift is off', () => {
+		expect(editor.currentPageShapes.length).toBe(0)
+		editor
+			.updateInstanceState({ isToolLocked: true })
+			.setCurrentTool('line')
+			.pointerDown(0, 0)
+			.pointerMove(10, 10)
+			.pointerUp(10, 10)
+			.pointerDown(100, 100)
+			.pointerMove(110, 110)
+			.pointerUp(100, 100)
+			.pointerUp(120, 110)
+		expect(editor.currentPageShapes.length).toBe(2)
+	})
+})

packages/tldraw/src/lib/shapes/line/toolStates/Pointing.ts

@@ -29,12 +29,11 @@ export class Pointing extends StateNode {
 
 		const shape = info.shapeId && this.editor.getShape<TLLineShape>(info.shapeId)
 
-		if (shape) {
+		if (shape && inputs.shiftKey) {
 			this.markId = `creating:${shape.id}`
 			this.editor.mark(this.markId)
 			this.shape = shape
 
-			if (inputs.shiftKey) {
 			const handles = this.editor.getShapeHandles(this.shape)
 			if (!handles) return
 
@@ -82,7 +81,6 @@ export class Pointing extends StateNode {
 					},
 				},
 			])
-			}
 		} else {
 			const id = createShapeId()