ColorEdit4: Alpha default to 255 (instead of 0) when omitted in hex input. (#3973)

Courtesy of @squadack

docs/CHANGELOG.txt

@@ -47,6 +47,7 @@ Other Changes:
 - Drags, Sliders, Inputs: Specifying a NULL format to Float functions default them to "%.3f" to be
   consistent with the compile-time default. (#3922)
 - DragScalar: Add default value for v_speed argument to match higher-level functions. (#3922) [@eliasdaler]
+- ColorEdit4: Alpha default to 255 (instead of 0) when omitted in hex input. (#3973) [@squadack]
 - Backends: SDL: Rework global mouse pos availability check listing supported platforms explicitly,
   effectively fixing mouse access on Raspberry Pi. (#2837, #3950) [@lethal-guitar, @hinxx]
 - Backends: Win32: Clearing keyboard down array when losing focus (WM_KILLFOCUS). (#2062, #3532, #3961)

imgui_widgets.cpp

@@ -4804,7 +4804,8 @@ bool ImGui::ColorEdit4(const char* label, float col[4], ImGuiColorEditFlags flag
             char* p = buf;
             while (*p == '#' || ImCharIsBlankA(*p))
                 p++;
-            i[0] = i[1] = i[2] = i[3] = 0;
+            i[0] = i[1] = i[2] = 0;
+            i[3] = 0xFF; // alpha default to 255 is not parsed by scanf (e.g. inputting #FFFFFF omitting alpha)
             if (alpha)
                 sscanf(p, "%02X%02X%02X%02X", (unsigned int*)&i[0], (unsigned int*)&i[1], (unsigned int*)&i[2], (unsigned int*)&i[3]); // Treat at unsigned (%X is unsigned)
             else