fix textinput infinite loop and panic

fixes infinite loop when deleting input that only contains whitespace
using deleteWordLeft()
fixes index out of range panic when deleting input that only contains
whitespace using deleteWordRight()

textinput/textinput.go

@@ -415,6 +415,9 @@ func (m *Model) deleteWordLeft() bool {
 	i := m.pos
 	blink := m.setCursor(m.pos - 1)
 	for unicode.IsSpace(m.value[m.pos]) {
+		if m.pos <= 0 {
+			break
+		}
 		// ignore series of whitespace before cursor
 		blink = m.setCursor(m.pos - 1)
 	}
@@ -457,6 +460,10 @@ func (m *Model) deleteWordRight() bool {
 	for unicode.IsSpace(m.value[m.pos]) {
 		// ignore series of whitespace after cursor
 		m.setCursor(m.pos + 1)
+
+		if m.pos >= len(m.value) {
+			break
+		}
 	}
 
 	for m.pos < len(m.value) {