Fix mutation of global state 'InvalidRect64'/'InvalidRectD'

by 'GetBounds' variants.

Author: ClaasJG

src/main/java/clipper2/Clipper.java

@@ -677,7 +677,7 @@ public static PathsD ReversePaths(PathsD paths) {
 	}
 
 	public static Rect64 GetBounds(Path64 path) {
-		Rect64 result = InvalidRect64;
+		Rect64 result = InvalidRect64.clone();
 		for (Point64 pt : path) {
 			if (pt.x < result.left) {
 				result.left = pt.x;
@@ -696,7 +696,7 @@ public static Rect64 GetBounds(Path64 path) {
 	}
 
 	public static Rect64 GetBounds(Paths64 paths) {
-		Rect64 result = InvalidRect64;
+		Rect64 result = InvalidRect64.clone();
 		for (Path64 path : paths) {
 			for (Point64 pt : path) {
 				if (pt.x < result.left) {
@@ -717,7 +717,7 @@ public static Rect64 GetBounds(Paths64 paths) {
 	}
 
 	public static RectD GetBounds(PathD path) {
-		RectD result = InvalidRectD;
+		RectD result = InvalidRectD.clone();
 		for (PointD pt : path) {
 			if (pt.x < result.left) {
 				result.left = pt.x;
@@ -736,7 +736,7 @@ public static RectD GetBounds(PathD path) {
 	}
 
 	public static RectD GetBounds(PathsD paths) {
-		RectD result = InvalidRectD;
+		RectD result = InvalidRectD.clone();
 		for (PathD path : paths) {
 			for (PointD pt : path) {
 				if (pt.x < result.left) {

src/main/java/clipper2/engine/ClipperBase.java

@@ -2778,7 +2778,7 @@ public static Rect64 GetBounds(Path64 path) {
 		if (path.isEmpty()) {
 			return new Rect64();
 		}
-		Rect64 result = Clipper.InvalidRect64;
+		Rect64 result = Clipper.InvalidRect64.clone();
 		for (Point64 pt : path) {
 			if (pt.x < result.left) {
 				result.left = pt.x;
@@ -2893,7 +2893,7 @@ protected void BuildTree(PolyPathBase polytree, Paths64 solutionOpen) {
 	}
 
 	public final Rect64 GetBounds() {
-		Rect64 bounds = Clipper.InvalidRect64;
+		Rect64 bounds = Clipper.InvalidRect64.clone();
 		for (Vertex t : vertexList) {
 			Vertex v = t;
 			do {