Prevent cursor position from becoming negative

Author: MatzElectronics

src/propterm.js

@@ -334,17 +334,14 @@ class PropTerm {
                 this.buffer.textArray[this.cursor.y] = '';
         }
 
-        if (this.cursor.x < 0) {
+        if (this.cursor.x < 0 && this.cursor.y > 0) {
             this.cursor.y--;
             this.cursor.x = this.buffer.textArray[this.cursor.y].length;
             if (this.cursor.x > this.size.charactersWide - 1) {
                 this.cursor.x = this.size.charactersWide - 1;
                 this.buffer.textArray[this.cursor.y] = this.buffer.textArray[this.cursor.y].substr(0, this.cursor.x);
             }
-        }
-    
-        if (this.cursor.y < 0) {
-            this.cursor.y = 0;
+        } else if (this.cursor.x < 0) {
             this.cursor.x = 0;
         }